We ate at Marrakesh and San Angel Inn and did desserts in France -- DD loved it all! She danced with the belly dancer in Morocco, watched the boats in Mexico, and loved eating 'fancy chocolate' in France. A few years ago I took my cousins (age 3 and 9) to Biergarten and they both loved the music and were more adventurous with the food than I expected... it's a fun atmosphere.
The best thing, IMO to make the dining experience good despite the age is to not push the time. We planned on eating earlier than DH and I would've done on our own to make sure DD wasn't past her breaking point. We found going right at 1130 when most places opened was good -- we usually were moving into World Showcase about that time anyway. For dinner, around 430 seemed good -- before the dinner rush and a good break if the day was REALLY hot.
Again, just my $.02, but we found DD was so caught up in the atmosphere she did better than we expected!