wynn, i went with my 5 & 7 year olds this past june. i strongly recommend a place with a kitchen so snacks are always available.
a pool is a must.
i took down a container of Quick so they could have chocolate milk, fruit snacks, and a box of cereal. my kids ate a lot of plain tortillas or pasta. if you ask, many places would make things plainer, like my kids got grilled shrimp or something. there is pizza available too.
trust me: knock JE off that list. i stayed there in '00. dont necessarily go by what you read. i got sucked in like that too.
i would recommend the palms, banyan bay, belizean shores, and i stayed at caribe island (and we thought CI was terrific). some are a little far to walk to town, but the kids thought riding in the golf cart was the coolest! (see linked pic!) http://www.pbase.com/image/3514735
ps - skip the thatched thing. as i said in a previous post, it isnt as cool as you'd think. stick with a condo. we did 2 br's. that was nice for us grown-ups. plus - bonus! - cable tv including Nick for 'downtime'.