Frustration

Why do I bother? I spent a month planning, organizing and reminding about a family friendly get together for the local poly group. I posted reminders all month, activities in the forum relating to the get together.
I spent time finding a date, getting prices and group rates. I gave plenty of notice and reminders. A few people said they might go, a few people said yes. Then, when I logged onto Fet today, ALL of the "maybe" people switched to "No" and the "yes" people switched to "no." And, why, you ask, would people suddenly switch from a family friendly poly family get together? Because the local public dungeon is having a party.
It is so frustrating to see all my hard work go down the drain like that. I had to cancel something I planned that everyone said they wanted, everyone asked for. But, no one wants to come because they cancel their family friendly plans to go to a dungeon party at a brand new dungeon that isn't even completely set up. Planning big events on days when other groups have events is not the way for a dungeon's leadership to endear themselves to a group. It will cost everyone $20 each to go to the dungeon party, I had the poly family outing where it would cost $5 each to attend.
This is just so frustrating, I don't know if I want to take the time to plan anything else for these people. This is the third time I have planned something that has not worked out. So I am at the why bother point.
I guess I am just done with all this drama.