oh my gosh Courtney I can CERTAINLY see how that would be VERY frustrating!
It would drive me nuts!
I would call them up and just let them know that if they can't go this weekend, you're gonna go see it with someone else, cause you really don't want to miss it in theaters and you've been wanting to see it for so long. it's polite and it's the truth! and if they still can't go, then go see it and tell them that you'd love to see something else with them when they're free.
Good luck! sorry this is such an issue!