Wow....285 is a lot! And this is coming from someone with roughly 60 first cousins. I don't even know how many second/third/whatever else cousins there are...they're always moving around too fast to count them all at family gatherings
But I'd never invite all of them to my wedding. I don't even think I could match up all of their faces with their names.
You can't count on people not showing up...they may surprise you!
I guess my best advice would be to set a level beyond which you won't invite anyone from the family (ie: no second cousins....or no cousins at all if you aren't particularly close to them). And...100 family friends?
I don't think I know even close to 100 people I would count as anything beyond an acquaintance.
Everyone has their own idea of what they want for their wedding. We're having about 30 people...only our nearest and dearest. But...well...I've been to a lot of weddings, and none of them had even close to 285 people on both sides, much less just one.