I do this diet for my son. It's so not as hard as you think, once you get your pantry switched over, meals become a no brainer. I'll address each food you listed first, then give you a bunch of blogs/websites to help you with meals so you have something to go by.
Meats: I buy all meat from a local farmer or from Whole Foods. You want to make sure you are getting grass fed beef.
Spices: I just buy organic spices from Target or other stores in my area, don't fret about the spices UNLESS, in the ingredients it lists flour to help with clumping.
Milk: My son enjoys Hemp Milk. You can find it at regular grocery stores or Whole Foods. It's my favorite when baking and for morning cereal. Also, a brand called So Delicious makes a "coconut beverage" milk that's really good.
Eggs: No worries, unless he has an allergy to the yolk or whites.
Cheese: We buy a brand called Daiya. It melts and stretches like real cheese. It's much better than rice cheese you'll find on the market.
Butter: We use Earth Balance (soy free version) brand. Our regular grocery store carries it. Tastes and acts just like regular butter.
Oats: We use Gluten Free Bob's Red Mill brand.
Lunches: PB&J ( I use Bob's Red Mill GF Wonderful Homemade Bread Mix) If you don't have a good bread maker with a GF bread setting, ler me know, I have two different ones and can tell you cons/pros of both.
Quesadilla: (GF tortillas from Whole Foods), Daiya cheese and mashed pinto beans. Serve with tortilla chips and favorite salsa and fresh fruit.
Homemade Chicken nuggets (if you want my recipe let me know)
Homemade Turkey Meatballs (again, let me know if you want the recipe)
As far as vitamins, my son is seen by a wellness doctor regarding his Autism so what he is on, is specific to his own symptoms. But if you really want to know, let me know and I'll list them off for you.
Now, Here are some websites/blogs to help you with mealtimes:
http://glutenfreegoddess.blogspot.com/
http://myaspergersgirl.blogspot.com/
http://www.nourishingmeals.com/
http://www.affairsofliving.com/
Hope that gets you started on a good foot! Other items I've found that may help are:
So Delicious cultured coconut milk Yogurts (my son loves the mango flavor!!)
So Delicious agave sweetened coconut milk ice cream bars
Applegate Farms lunch meats
Applegate Farms Turkey Bacon
K-Toos cookies (like Oreos)
Oogave Root Beer (Yes, your child CAN have root beer floats!)
Envirokids Cereals
Oh, while I'm thinking about it, has your son been tested for any food allergies/intolerances? If not, go do that first just to make sure some of his symptoms aren't a result of eating foods he really shouldn't. My son has an allergy to garlic, I would never had know that and after I removed it, it's amazing how some of his symptoms cleared up:)
If you are lost and confused, send me a private message and I can definitely help you as I've been on this journey of a gf/cf diet and other biomedical treatments for 3 years now:)