Just a thought for the awesome playground you're making for our school! How to Make an Outdoor Chalkboard- What a fun outdoor activity for the kids! Full tutorial includes list of weather proof materials!
Outdoor shower/water day for kids.Could easily be made with hollow box uprights, run the water tube through one and the top hollow box with a PVC tube that you drill holes in for the water to run out. Faux paint it to look like copper, really pretty easy.