I agree, I think Chef Mickey's on your arrival night is a good plan. We are always tired from our travel day and we like to get to bed fairly early so we can be full of energy the next morning.
I would recommend the Hoop Dee Doo Review as well. It is a dinner show set to a Western Theme. The show is full of singing, dancing, corny jokes and audience participation. The food is good "Down Home" cooking, not gourmet for sure. The meal is fried chicken, ribs, corn on the cob, mashed potatoes, salad and bread, with delicious strawberry shortcake for dessert and is all you care to eat. It also includes beer, wine and sangria. We think it is a blast for all ages and highly recommend it, if you like this kind of thing.
Kona Cafe is one of my favorites, but they have changed the menu since I was there last.
'OHana is good and will be fun for your nephew. If you time it right you can see Wishes from the windows. It is a wow.
We love Teppan Edo in Japan. The chef cooks and performs at the grill at your table. This should keep your nephew entertained, and the food is delicious. These are tables for 8 so you will have others seated with you.
We loved Jiko for an upscale dinner. The atmosphere is beautiful, the food delicious, the service great and they have an outstanding South Africian based wine list.
We ate at the 50's Prime Time in the Studios in October and we totally enjoyed ourselves. Again, this is "Down Home" cooking but it was really good and it is a fun atmosphere.
We love the International restaurants in Epcot especially Restaurant Marrakkesh in Morocco where a Belly Dancer entertains, Le Cellier, the Rose & Crown Pub - ask for a patio seat to see Illuminations if you are lucky, and this past trip we ate at the San Angel Inn in Mexico and it was very good.
Good Luck with your planning