X-Mas Dinner in or around Irvine
If I'm not mistaken, Five Crowns in Corona Del Mar is open on Christmas day. I'm having a hard time thinking about what may be open in Irvine proper, except Mimi's Cafe. For buffets, you may have to look at the bigger hotels nearby, like the Hyatt, Marriot or Island Hotel.
3801 East Coast Highway, Corona Del Mar, CA 92625
4030 Barranca Pkwy, Irvine, CA 92604