There are other options worth exploring if a separate, staffed room isn't available or within your budget. Kids who are distracted, kept busy or entertained in the main event area will be much better behaved than those who sit idle at the grown-ups table and get bored.
Consider hiring a balloon artist, caricaturist, clown or magician to entertain kids in a designated corner of your reception room. Just don't let the magician abracadabra away the bride's bouquet!
If that kind of specialty entertainment isn't in the budget (and none of your friends will volunteer to don a clown suit for a few hours), opt for some low-brow fun. Kids can also be remarkably distracted by a few strategically placed activity tables with non-messy crafts, board games or toys. For a seated dinner with several (read: booooring!) courses, provide activity sheets and crayons for children to color between courses. Or, cover the kids' table with butcher paper and let them draw on the "tablecloth." Talk about fun!