A few simple rules for people who get invited to a child's birthday party, especially if it is at a paid location rather than at somebody's house:
1) RSVP prior to the RSVP date. Not the day after the date, not the day before the party. Just let the parents know if you're coming or not with enough time to plan!
2) If your child is invited to the party and you want to bring your other children along, ask if it's okay. Don't just assume you can bring your other three kids and nobody will care. Many locations have an upper limit on the number of children that can come to a party.
3) If you RSVP that you are going to the party, go. If you RSVP that you're not going (or not at all), don't go.
4) Don't say something like "we might be able to stop by." Are you aware that these places charge $20 per kid sometimes and need to know in advance?
5) Just bring one present. Who started this precedent of every family bringing like three presents? My kid has enough toys already.
6) Do not leave your kid at the party unless you are explicitly told it is okay. If your kid is under five years old, it is probably not okay. The last thing I need to deal with when running a party is your kid sobbing because he can't find you.
I hope kids appreciate how stressful these parties are for the parents…