Sorry to hear of the lack of crappie - hope the kiddos had fun anyhow just getting out.
This time of year is tough for crappie as they seem to be worse than normal about shutting down due to: weather, rain, fronts, lake level rising or falling, woke up on the wrong side of the tree or whatever. Un-predictable except that when they do come shallow and settle down you can catch a bunch right off the bank (sometimes)
A lot of guides don't like this time of year for crappie fishing for above reasons and are much happier when they get into their regular predictable summer pattern.
Next time you take those kids out, get yourself about a 100 live crickets in a wire cricket cage and some long shank size 6 cricket hooks. Bluegill can be a blast and not uncommon to get enough big ones to make a meal. I filet the ones over 7" just like they were a crappie and they are sure tasty! There is always the occasional (or almost every cast) catfish depending on time of year.
Lots of 14" channels and you never know when a 13 lb flathead might be hungry for a cricket snack. That'll get them kids jumping and hollering I'll tell you.