I'm so excited for you for this project!!!! I definitely think you have an added challenge with the covid situation, but as long as all the events are outside and you try and put things in place for social distancing: "this is your spot, until I say go you have to stay in your circle, and when I call freeze you have to get back into your spot as soon as possible", as well as contact tracing for if/when the dreaded happens: "today, your group is Suzie and Sam. You are going to do the experiment together, and I don't want to see any of you going into another group today. Next week you get a new group"
The older kids are going to be better about wearing masks etc, but your whole agree group is old enough to wear masks and I would advise that you begin and end each session by doling out squirts of hand sanitizer, and I think all of that will go a long way.
You're doing valuable work helping out what could potentially turn into a "lost generation" depending on how societal recovery from the covid situation goes, so major major MAJOR kudos to you.
Here's an idea: why don't you put up a Kickstarter or gofundme for your club, and hopefully folks in the neighborhood (as well as here!!) Will help you pay for supplies