M.S.
I personaly wouldn;t worry about it. I stopped doing thank you's for b-day parties because I felt it wasn;t worth the hassle. I tell everyone thank you while they are there and how much I appreciate them. You could just call the few that you feel like telling them personaly and tell them how much the kids enjoyed whateverthey got them and thank them for coming. But if not, I would say bye bye to the thnk you cards.