The servers don't mind if you split a meal, in fact that's the advice I give at Mythos. You can tell the server you're saving room for desert, just tip them well. Kids menu usually has a cut off age of 12, but again, the server isn't going to ask for ID or anything like that.
At Mythos, they give you free bread to start, and a good item to split is the wrap of the day or a cowboy burger. If you scroll near the bottom of this page you can see 4 items at Margaritaville.
Portofino Bay Hotel
Another idea is to order an appetizer and let the kids share. I've heard the volcano nachos are good. Just tell the server the kids are going to share an app, and then you give them bites of what you're eating.
It's nice to look at the menus and plan where you want to go, but I wouldn't be obsessed with it. Some people visit the restaurants and expect the world. You have to remember the number of people they're serving, it's a lot. The food is good, but don't set the bar too high or you'll be frustrated and it will ruin your trip.