Giselle's advice is really good!

You might also want to start her in Obedience classes (if you haven't already), and practice a solid down-stay. Have her down-stay while the kids are having a snack or you're eating, and when everyone is done (if she hasn't broken her stay) give her a special treat, a bone, a stuffed kong, a greenie, etc. Also have your kids never offer her their food while they're eating. Crating is also good ^_^. . . we have to crate Gonzo for dinner, and he eats his food in his crate, because my little brother is only 2 1/2 and doesn't understand why the dog shouldn't share his food