H.L.
Unfortunately I think you have to foot the bill unless you'd somehow made it known upfront you weren't. I did for my husband's 40th bc it was a "party" I was throwing so how could I then expect other people to pay? I don't ask people to chip in for a party at home... Likely they will bring presents since it's a big bday and you're making it an event. So that's their contribution. In terms of separate checks, I guess it depends how your friends do things. We have never requested separate checks even when we're all going to chip in. It would be considered very tacky and in a way insulting. In this case, it would be even worse in my opinion because you invited everyone to a party. Also, as a former waitress, separate checks are a huge burden and in a nice restaurant, sometimes not even allowed.