Hi lisateaches!
We have a similar age difference between our middle and youngest son, and I think you've made some great choices!
I'd take the earliest CP ADR you can get, so that you can enjoy the less-crowded early morning time at MK. So I'd definitely go with 8:20am.
Our boys all love LTT for lunch! If your kids are used to eating after 1pm, sounds great. For our boys, we usually have ADRs at 11:30 or noon because that's when they usually eat at home.
I wasn't sure about AH, but is that Akershus for breakfast? Again, if you could get earlier in the day, you could eat before the park opens and take advantage of the less crowded morning hours at Epcot. But if your kids are used to a later breakfast and you hit some of the more popular Epcot rides immediately after a 9am opening, that would work.
We haven't been to Teppan Edo, but we have friends who absolutely love it! If you're trying to balance out the morning breakfast at Akershus, that would work.
Garden Grill is our boys' favorite restaurant and our arrival night tradition! It's great for all ages, and a really festive way to end your trip. I think the 5:20pm time would work well for a toddler/pre-schooler. We try to make ADRs at 5:30 or 6pm so that our youngest doesn't get too crabby at dinner.
Hope you have a great trip!!
