Remove any extra knots in the painter. They shorten the painter. They weaken the painter. Catch these knots at the end of the first day they're formed and they'll be a lot easier to remove than if they sit for a season. Put absolutely NO hardware at the end of the painter.
Shackles placed there can cause terrible injuries if a painter snaps.
Reduce the number of boats in your tow - five max in each line. The race to the dock, spewing roostertails, may be exhilarating for the kids but it carries two dangers. First, it increases the risk of snapping a painter. Second, it increases the severity of the injury that would result by the heavily loaded painter. Have the skippers in your tow sit forward in their boats to reduce drag.