Glad you found the problem. It probably isn't a good idea to put the attenuator right on the driven element anyway. I worry when people put anything in the space between reflector and driven element, and also when they hold the antenna by the boom between reflector and DE. I'm sure that this proximity adversely affects the antenna performance, especially on 70 cm. I encourage people to mount attenuators and receivers behind the reflector and to use some sort of handle so that the holding hand isn't inside the beam.
It's great that you are doing the demo at church and I hope that the kids can try it for themselves. On Saturday, we'll have a dozen or more transmitters in a park in Long Beach for the Scout-O-Rama. If it is like years before, there will be so many Scouts that it will keep five hams busy all day giving the kids a chance to hunt two or three of them each.
If any of your kids show an extra amount of interest in foxhunting, tell them about the ARDF events we have here in soCal and encourage them to come out. That's how we got Monique, the 12-year-old girl who went to the USA ARDF Championships last year.