Pretty much all the sit down restaurants can accommodate larger parties, but here are some suggestions.
Parks:
MK:LTT, Cindy's (can be difficult), Tony's
EC: All the WS countries, Germany only has large tables, Coral Reef
ST: Mama Melrose, H&V, 50s Prime (Might be tight), Brown Derby
Resorts:
Concourse, CM's, Whispering Canyon, Artist Point, Hoop Dee Doo, Ohana, Kona, GF Cafe, 1900 (tight fit), Cape May, Yachts St, Flying Fish, Jiko, Boma