Bring back the monkey bars, climbing rope, horizontal ladders. Kids are lacking upper body strength big time. God help them if they ever fall out of a boat and have to hang on for more than a minute.
Do you have the space and budget to build an obstacle course? Maybe you could design it with stations that could be easily adjusted or modified to as to change it up every couple of weeks.
Try tires. I got a girls softball team that thinks they're the cat's ass. They flip tires around the bases. We have relay races flipping tires. They all have sandbags. With a rope handle the sandbag converts to a "kettlebag" or is it a "sandbell".
Just mix it up, As you probably know, they get bored easily. Don't be afraid to set the bar high.
Keep everyone posted on your progress and how the kids respond to new stuff.