Under $15 p.p."something different" for large group O.C.
(1) Have you been to The Royal Thai (locally in Newport Beach and Laguna Beach)? It has been there for decades and they haven't changed the recipes much. I always liked the Newport Beach location better (and it is more accomodating of large groups. Their food is delicious. I have even taken cooking classes there. Their Tom Kha Kai soup is a delicious starter and would be totally filling for a small appetite. Many curry dishes., good vegetable dishes, and duck. A plate might be $15, but will be generous, IMO - eat family style and try many tastes.
(2) Another suggestion:
How about Persian food at Darya in Costa Mesa? They don't mind large groups, but do charge a mandatory tip for parties over 6. They also have a split plate charge, but you can get around that if you want by not asking for another plate (too tacky?). Portions are generous enough to share, IMO. Menu is quite lovely, fresh and healthy.
There is also a Persian restaurant in Irvine that is really really good, but I think it is a little more expensive. Still, the dishes are plenty, so split a few between people and you might be able to stay within budget. I haven't been there fo a while, but they also have evening entertainment, bellydancing, on busy nights.
(3) Another place that serves family style is The Spaghetti Bender in Newport Beach. Their table-top minnestrone in a turreen is great, their gnocchi, and their homemade mayonnaise salad dressing. Portions are generous, so share one with another. Not all menu items rate, but if you're in the mood for a turreen of minestrone and good bread this winter, enjoy it.