We gravitate toward Disney buffets just so we can get ANY healthy food into our two little guys, but I understand not wanting to pay so much when they only eat a thimble-full! One of ours still eats free though.
We had a wonderful moderately priced meal at Kona Cafe in the Poly. The waitstaff was wonderful to our kids too. It was a highlight of our December trip. Haven't tried Ohana yet - very much looking forward to trying it!
Here are some other places my 4-year-old gave a thumbs up to:
Whispering Canyon Cafe in WL - really, really fun!
Garden Grill (think it will still be closed when you come though, foodwise this was his favorite)
Liberty Tree Tavern in MK (it's plated all you can eat, but very basic stuff like turkey, mashed potatoes, mac & cheese - think Thanksgiving dinner),
Spoodles on the Boardwalk (pizza and things to dip, always a pre-schooler hit)
Beaches and Cream at the Beach Club (I think the entrees are terrible there, but he loves it. Ice cream sundaes are fantastic though)
the buffets Boma, Hollywood & Vine, Trails End (super cheap for a Disney buffet and homestyle food) and Crystal Palace for the many choices.
We haven't made Teppanyaki at Epcot's WS yet but, looking at the menu and hearing from others, I think it will be a hit - teriyaki chicken and rice, that kind of thing. I've heard mixed things about both 50's Primetime & SciFi at MGM so we haven't tried either. Besides, I think my kids would be scared of the film clips at SciFi at this age. Also, bear in mind, if you are ordering a kid's meal or two, the menus at most Disney restaurants are the same. So look through the menus on allearsnet.com and pick the places YOU want to eat, knowing that, if nothing else, your kids can get the old (mostly unhealthy, unfortunately) standbys mac & cheese, chicken nuggets, etc. in a pinch.
Good luck and have fun!