I'd recommend the Rose & Crown at the UK pavillion & the Garden Grill. I've dined at Coral Reef and it was ok. The food was a little pricy, but the atmosphere is great.
I would also strongly recommend Spoodle's at the Boardwalk (EXCELLENT!!), the Yachtsman Steakhouse at the Yacht Club and Beaches & Cream at the Beach Club. The last one is much more casual, but I think the kids (& in-laws) would enjoy the old-fasioned ice cream parlor look to it. If everyone is big ice cream eaters, maybe you all could split the "Kitchen Sink" one day. The looks on the kids (& in-laws) faces should be classic!