Given that it's so far out and on a holiday, it might be a good idea to split your guest list into "A" and "B". Then if a bunch of people on the A list say they can't make it, send out invites to the B list until you fill your quota. Like, if all your friends from LJ can't make it, you can start inviting your dad's aunt's cousin's college roommate's kids' babysitter's boyfriend, or whatever.