need help...

ok so my inlaws never gave us a wedding present. yeah i know, but they are hurting for money. so mil says that she still has to give us our gift.... so i was joking around and told them im gunna hold their thank you hostge intill we get it and everyone else in the house cant show her the picture, and shes soo totally kool with that, but i cant not send one to them.

so my question is what do i write? they paid for out invites and the RD. i have to send them one, i feel like a a$$ if i dont, so what would you write?

thanks!