For quick service in the parks, we really enjoy Mel's Diner (50s diner style with vintage cars out front) Decent burgers, chicken strips, fries, and excellent hand-dipped milkshakes...that's in Studios.
If we are in IoA, we go to Captain America's diner (we are huge super hero fans), it's got a fun decor of giant Marvel cut-outs. Again, decent burgers, chicken strips, fries.
I think these are slightly pricier, but a lot of fun: Three Broomsticks (IoA), Leaky Cauldron (Studios), and the Simpsons food court (Studios.)
Theme parks, of course, are usually pricier than at home places, but some of the table service places aren't that bad price-wise either. We always go to Finnigans during our trip (Studios), not a "fun" place, but great food & it's right next to where the Blues Brothers do their show in the street. We like to get a table near the show, if it's going on, and watch while we eat.
Margaritaville (in City Walk) is decently priced as well and can be a lot of fun. They either have live music on the stage outside or piped in music. We sit on the patio & people watch. Usually there are stilt walkers that roam around the tables and make balloon creations for the kiddos.