It really is up to the child and what they like each country has something, most have movies that explain that country, some ( 2) have rides.
If you do the movies, and spend 10 minutes looking around ( there are 9 of these) that would be 180 minutes ( if the move take 10 minute,) and do not forget about the live interveners out side like the drums at China or the flags at France ( I think) or the singer American.
I would really plane on a water noon for this ( 3 or 4 hours maybe more ) if you get done you can go do some thing in the WS or maybe back to your hotel to swim