Bah, Humbug - I hope all you grumpy McScrooges are staying home for Christmas Dinner
We've gone to Beachcombers the last couple of years with all the family visiting and children in tow. The food seems to keep everyone happy and we ask for a table outside - the hooligans are then free to run around on the sandy area away from everyone or the grassy area as long as we can see them. That rule is pretty redundant though as the adults of the group invariable start/join in a game of footie!
Felix is right, for the more popular places or big tables you need to book in August and pay in October - we managed Beachcombers our first year only because people didn't cough up the cash in October.
If family are booking flights then why not book a table to be sure??