I was headcounselor as well, and when we had long time slots, we generally prepared activities with a few steps. for example, we set up 4-5 different centers, each center had another activity/game. the kids would go to each aactivity for 5-7 minutes and then the hc would blow hteir whistle and everybody would move to the next center.
Another activity we prepared was a hunt with something atttached to it. EG we would hide watermelons- ( dress as a baby and p ut in a carriage) and have each bunk find them. once they were found, the bunks needed to create something with the watermelon, based on a theme…
Good luck!