K.,
I've been homeschooling for almost 10 yrs, and I think the stage you are in is the hardest. It does get easier! At 5, your kindergartener is just getting used to the discipline of schoolwork, and it's natural for her to get distracted by her sibling. She doesn't need to do a lot of formal schoolwork at this point. Maybe a bit of math (and even that can be fun...I recommend RightStart Math, which has lots of games and manipulatives), and some phonics and early writing work. The rest can be nature study (go for walks!), easy science experiments, and TONS of reading to both children. Some days you won't get a lot done. That's ok :). Relax, have fun, join a couple local homeschooling groups (field trip groups are great). Think about what your child enjoys, and then incorporate that into her learning (my son once told me to change his math problem from counting frogs to counting Star Wars rebel fighters!). I recommend Creative Homeschooling, A Resource for Smart Families (Lisa Rivero) and Home Learning Year by Year (Rebecca Rupp) for you to read. As others have said, include your 3 yr old in some of the learning, and give her other 'work' to do also. My 3 yr old does his best to distract his three older siblings, but he's gradually accepting that they can't play with him when they have schoolwork to do. I wouldn't recommend videos for the the 3 yr old while the kindergartener is working. We have a TV off rule while anyone is working on schoolwork because they all get distracted if the TV is on. Occasionally, they all watch an educational video, but I usually save that for afternoon. Timers work well too. Set a timer for 1/2 hr and tell the children that you will work with the 5 yr old while the 3 yr old works independently. When the timer goes off, they both get a treat (food or special activity). Just spend a lot of time doing informal learning and enjoying the time with them. Give yourself credit for taking on homeschooling and give it time to work. If you have any questions, feel free to email me.
H.