I'll list my sons favorite dining spots when they were preteens. All of these are cheap eating places:
At
Universal:
Mels Drive-in: hamburgers and shakes--food isn't too great for adults but the kids love the 1950-60s rock and roll atmosphere
Louie's Italian Restaurant : Pizza, pasta, espresso bar, and Italian desserts.
Monster cafe: Monster salads, pizza, pasta and desserts but the kids enjoyed watching the old monster movies on the tvs there and seeing the movie props. Food is Ok for adult tastes.
Richters: Hamburgers and all the fixin's--- much better hamburgers than Mels. Hamburgers even the adults like.
Captain Quint's Seafood and Chowder House Restaurant : fish, seafood,and chowder--counter service, picnic tables to eat outside and great view of the lagoon and park.
Islands of Adventure:
Enchanted Oak Tavern: This was our family's all time favorite place to eat. BBQ ribs and roasted corn on the cob is not to be missed. My son's loved the hamburgers. Here's a menu with prices:
http://www.ioacentral.com/islands/the_lost_continent/restaurants/enchanted_oak_tavern.htm
Burger Digs at Jurassic Park: the name says it all.
Confisco: menu and prices at :
http://www.ioacentral.com/islands/port_of_entry/restaurants/confisco_grille_and_backwater_bar.htm
At
Citywalk:
Nascar and Hard Rock Cafe (HR is not what I would call inexpensive though)
I'll post about ride recommendations later. Meanwhile for a great look at all the rides go to
http://www.ioacentral.com