We have open adoptions with our 3 children. We have the extended birth families over often for special occasions, not just the BMom's. We have no contact with any BDads.

We celebrate birthdays with ALL our family, my side, Dh's side & BMom & her family. We told our children's BMom & Family that we weren't just adopting their child, we were adding thier WHOLE family to ours!
GOOD LUCK!! I hope your celebration goes GREAT!!!
Deb