I also put no children and costumes mandatory, I've been pretty lucky with the no kids. One year a friend drove 2 hours to come to the party and shows up with her son. I had a couple there who had been quite upset that they couldn't bring their 2 little girls and I was really embarrassed. I saw daggers in her eyes. We made it quite clear to her that we had no idea and were upset ourselves. Actually she then felt sorry for us and gave our other friend the look all night and the other friend has never brought her son again.
heheheh
As for the costume requirement, that's another story! I gave up putting required on the invites because so many people wouldn't wear them. But it p/o's me so much that I'm putting it back on this year! Bwahahahaha! With a side note that those who don't come in costume will be "costumed" at the door! Years ago someone at my job had a party and the people who came without a costume got Halloween hair spray and makeup put on them at the door. I recently had that memory suddenly come to mind, out of the blue, and it was like BAM that is what I'm gonna do!
I know who to put in charge of it, too. Our youngest son and his g/f, they are 21 and 22 and love Halloween and hate it when people don't get into the spirit.