i know what you are going threw! two years ago i was remarried (it was his first). all of his family showed up, only one uncle out of 12 aunts and uncles showed up and only one cousin showed up... out of over 50+ family members invited. they all said they other plans or something came up. i was really hurt by it all.
then we had a baby shower ( i got pregnant on our wedding night actually!) and only 3 showed up for that... to a point i understood because this was my 4th baby.. but it was my husbands first. but i was still really hurt!
(there was no other family get togethers between our wedding and the shower)
for us the next time the intire family got together was for my uncles funeral (i was induced 2 days before my due date, got out of the hospitial with him and drove right to the funeral). he was killed in a motorcycle accident.
so my advice is to go to this! you just never know when it will be the last time you get to see one of your family members or when it will be the last time the family gets together. you don't want to be holding on to some anger or grudge and have something like a death happen then you are dealing with the guilt of not going.