Aw Katy you're not having much luck with this are you.
Get a DJ and stop thinking about the people who can't make it and start thinking about those who can. I like smaller numbers because it feels more exclusive and you get the chance to chat to everyone.
My 40th was the biggest wash out ever. We were supposed to be going to Venice just dh and I. We ended up doing a trip to London with all four kids. The low point was sitting in a posh restaurant and noticing a pool of Diahorrea building up under my baby son's high chair as we ate.
So whatever happens, you'll have a better time than that.
May I be the first to wish you a happy birthday and if it's guests you/re looking for feel free to email me.