FMIL just sent me a FB message telling me that she would like to pay for the 10 rooms we have reserved at our venue. I think it's very generous, but I'm trying to figure out how this is going to work out logistically before responding. I see her vision - OOT guests will not have to shell out $$$ for the room on top of travel expenses. But I can see our college buddies getting their STDs and calling the hotel and finding out that the rooms have been taken care of, leaving our OOT guests SOL. How do I respond without sounding too negative or ungrateful (because I'm blown away by this act of generosity - she is going above and beyond)?