UGH!!!!! Isn't it infuriating?? WHAT is up with people these days?? It seems hard to believe that so many were not raised with any proper manners, but alas, it's true.
So that my children know better - if they take their time deciding whether or not they want to attend a party, I make the decision for them by the time it's five days before the party. And the decision is that they don't go. They have been upset and disappointed that I RSVP'd as a no, but they have also learned that they need to make their decision quickly once receiving an invitation. They also (this is another area where parents are rude) have to write their thank you notes BEFORE they are allowed to play with any gift they receive. Our thank you notes now go out the day after the birthday or Christmas! :)
I plan/coordinate/run birthday parties at my business. The last one I had was a tea party theme. I had already bought all of the favors, the china tea cups, the prizes, etc. On Saturday morning, at 10:00, TWO HOURS before the party, I received a phone call from a woman saying, "This is Stephanie's mom. She's coming to a birthday party there today, and I guess I'm supposed to RSVP or something...?" Really? REALLY? I was practically speechless, I was so appalled at her rudeness.
Anyway! As you can tell, this is huge pet peeve for me! :)
Although I know what you'll need to do is call everyone and ask them, I WISH you could do something like hold the party elsewhere, so when the rude people just show up at your house, you're not there! Or, when they show up, act really surprised and like you're not sure what to do now and make it awkward for them - "Oh, HI! I didn't hear from you, so I didn't know Sophie was coming. Um, shoot, I don't know what to do... I only have enough goody bags for the children I knew were coming........"
Good luck!
J.