I have created 15 circuit activities that are all mostly school related for the children to have fun. I posted these all around the gym with all of the equipment ready. If you collaborate with other junior and/or primary teachers, you could all do circuit training at once so the equipment stays out for the entire day ready for the next teacher.
You could print out these pages and tape them to the wall for the children to read the quick instructions and then they can continue.
I hope you enjoy them as much as my class had. :)