The MOST important thing to remember about Homeschooling is this: Homeschooling is EASY. It's PARENTING that's hard.
Like good parents, good homeschoolers I know question themselves. They ask the same questions that you're asking, and they do it fairly frequently... constantly reevaluating. They look at their children's learning styles and interactions with both themselves as teachers and with the other teachers in their lives (tutors, coaches, instructors, directors, etc.). I would be FAR more concerned about any parent or teacher who DIDN'T question their own abilities.
A few things to consider:
1) Just because you homeschool doesn't mean that you are the only teacher. As you said... there is your mother. BUT there are also a plethora of opportunities for outside education. I even know some HS'ers who NEVER teach, but "farm" everything out. For my son... we farm out art and music. He's also in the "school break" camps that happen year round. Here's a short list of ways in which a HS'er shares teaching responsibility by (in addition to being their child's teacher) as their facilitator:
- Outside Classes (art, music, science, languages, history, english, etc. )*
- School Break Camps (our kiddo like to alternate between drama, science, & sports camps)
- Online learning (the ranges from interactive websites - like discovery, discovery.edu, starfall, nat.geo.soc, pbskids, + 100's of others...to "virtual tours" of museums, archeological digs, etc... to organizstions like museums, govt agencies, etc that have online free educational pages for kids... to to actual online curricula like Plato Sciences, Time for Learning, etc)
- Computer "games" (Learning shouldn't be fun, should it? Seriously, games are a *tremendous* asset. 3 of our current/long term favs are ClueFinders, Carmen SanDiego, iSpy)
- Seminars & Field Trips (One off classes taught by orgs like Observatories, Museums, Factories, businesses, hospitals, universities... plus getting friends involved for having your child come be shown what they "do". We've had filmmakers, sound techs, a rabbi, computer programmer, video game designer, military, chocolatier, waitress, car mechanic, and a highschool kid really into robotics all take kiddo over the past 3 years to do projects with them. Learning happens EVERYWHERE... and seeing how real people utilize the skills he's learning, or teach him new ones are... just amazing opportunities. School really comes to life. And for kids, it's all exciting, whether it's a "sexy job" or not... because it's in the adult world, and they get to be a part of it)
- Movies (Yup... I will eat ramen before I cancel my netflix subscription. The documentaries they are making these days are better than The Matrix. I'm a pretty killer science teacher... but I'm no Carl Sagan or deGrasse Tyson... I also can bring dinosaurs thundering across the screen with the BBC, or make child-appropriate clips from dozens of amazing historical fiction. Troy is the most recent one, since we're studying Ancient Greece... but there are also such classics as Magic School House, and hundreds and hundreds of other titles that are all either educational already, or bring a 2 dimensional lesson to vivid color & 3d)
- Co-ops
* Just to note on outside classes. You can find tutors for individual subjects, but I personally prefer actual "classes". Music, Art, & other "electives" are easy to find. But for english, science, history... I tend to find they're advertised by speciality. Like shakespeare for Eng., or Pirates for history, etc. These classes are all over the place. GoCityKids or ParentsConnect are starting to make them easier to find, plus there are Homeschool Co-ops, Community Centers, Science Centers, living history museums, private companies...YMCA even does them as part of their "Kids University" after school program. In fact, MANY of these classes are found by looking up "after school" programs. We're doing Shakespeare this fall for "english" that's actually through a kid's DRAMA program.
2) SCHEDULES. Depending on how you look at it, we either HS 7 days a week or HS 4 days a week (we "unschool" over weekends and holidays and breaks). Most HS'ers are pretty similar in that they tweak their schedules to work with their own families instead of following what the schoolboard outlines. A few do 5 day weeks, but not a lot. There's no law anywhere that says that "school" can only happen M-F and must be from 8am-3pm. We do school in the car, at night, in the swimming pool, on hot chocolate breaks while snowboarding... at the dining room table, while on "vacation". You're already home 4 days a week. I don't know PA law (easy to look up), but there's no reason you can't do a 4 day week if your mum doesn't want to take on 1-3 days herself, even if PA requires a 180 day year. It just means doing school over the summer. Which I personally prefer anyway.
3) "BEST" takes awhile, and it's hard. Okay is easy... it's everywhere. My son can do well in any kind of schooling environment. Public, private, home, boarding. Pick a schooling system and he can do well. He could even excel and be happy in certain cases in EACH of those systems. But best? Best is elusive. We HS... so we look for best in THIS system... which is easier in that I'm not relying on others, and I can tailor to suit my son to a certain degree... and harder in that I'M the one who has to do the observation, footwork, research, and implementation (but that's also kind of fun). Homeschooling we've had good & great... but we've also had "Well THAT doesn't work" moments... and even had a "good" turn into a "best" by completely changing what we were doing to something else. And I've had what I thought would be perfect fall flat on it's face. It's all a learning experience. But schools do that as well... no one single way suits all kids... so they AS WELL AS WE are constantly experimenting. But they have to do it on thousands of kids and go off of percenetages as x % gets it this way, y% gets it that way, and they work on decades. We get to do it one on one, and can adjust without the approval of school boards and parents. ((HS joke: "What do you call a HS parent talking to themselves?" ... "A parent teacher conference"))
So take the idea of being his "best" teacher... and toss it out the window. You'll be best at some things... and not at others. You'll be the entire range from mediocre to good to great to best... but it WILL be a range. NO ONE is best all the time. Then you add in curriculum, and "best" really becomes a JOURNEY. Sometimes you luck out. Sometimes it takes awhile. Sometimes "best" changes. It's all very fluid.
But by MERELY seeking to be your best, and by paying attention to how things are working with your son... you'll be phenom. We all want the best for our children. But the secret is... none of us can do that 100% of the time. By HS'ing you're taking "best" under your own control, instead of crossing your fingers and hoping someone else will be. Even when you're farming stuff out, you still have control... because you can drop the class or the teacher if it's not going well. Rather impossible to do in Edu elsewhere until you hit college.
4) SOME useful links
http://www.homeschooldiner.com/guide/intro/approaches.html
http://www.homeschooldiner.com
http://homeschooling.gomilpitas.com/ (the content is on the left, commercials on the right)
http://groups.yahoo.com/ just search Homeschool + _________ (PA, Secular, elem/middle/highschool/etc., philosophy, etc.) for some really great "in the trenches" message boards
And here I went and wrote a "book" again. Sigh. Sorry. But as to your original Q... can you handle it? No way to know without trying. Can the 2 of you HS together? Of course! You're "responsible" but just see #1 for short list of teachers available for you to utilize.