I don't know of a shapes collection for this kind of drawing. I guess you have to create your own.
If you create proper shapes, you'll have to do this only once, and can place those shapes in stencils afterwards for later uses.
I think it's a nice idea for planing a camp but don't push it to far. I remember a scout leader who calculated everything that had remotly to do with our camp. He even calculated how many pieces of toilet paper kids should use for the average visit at the latrines. And he raised hell after 2 weeks when it became clear, the toilet paper won't last for the remaining third week of the camp.
