your family understands you have issues with food i am guessing. it may be easier to explain to them why you aren't eating that much.
simply take a small bit of 3 to 5 side dishes and normal amount of turkey. remind yourself this is a family outing of sorts and you don't do this everyday. one day of eating more than what you usually do will not kill you.
if there is a 'kid' table, to offer to sit over them and watch them. at my house there was an adult that hovered over the kids but did not sit with them. this would allow you to keep an eye on the kids while not feel you are being watched at the table by everyone.
if you do not feel you are able to sit at the table with everyone and not overeat, maybe skipping eating at the dinner table would be good. if there is a place you can eat other than at the table, it may help you.
these are several suggestions i came up with over the years of dealing with the holidays.
it's funny, i just said to my hubby yesterday how scared i am of xmas, especially spending it with my family.
but i guess i'm lucky in a way as they seem to know by now that i really need to do my own thing with food. but it is so **** hard to have your little bits while everyone keeps on eating and drinking and then later the comments about how full everyone is and oh, that feels sooo good. ugh!
what usually helps me is simply helping out with clearing and cleaning dishes, serving, basically taking car of others and make them feel comfortable. and it means i can stay on my feet after i ate and not think too much.
all in all though, i feel that during those times ED is louder than ever and even though i might not give in to b/p the whole restricting part is strong as hell.
so should this be a time to fight ED too? maybe by eating something you wouldn't usually allow yourself?