I'm with Aunt on this. Also, realize that anyone who travels will have to take off of work 2 days - they may not have the ability to do so or the time.
And even local people will have to take off AT LEAST a half day to make it if not a full day.
Personally I'd find it very inconvenient and if it wasn't in my immediate area would end up declining.
Also, I don't know how big your WP is, but are you having a rehearsal the night before? Are you going to expect them to take off of work early the night before AND the day of? That's a lot to ask especially if they don't have vacation days.
But if you do what AOTB suggested then at least you know your must haves will be there.
Although I'd personally look into cutting the guest list and having it on a weekend or even a Friday night which would require most of your OOT guests to only take off a day of work.