Hi, D.! We JUST finished our bakcyard play area and I was toiling over the very same thing! We ended up going with pea gravel to fill the area, and so far we love it. We had our "grand opening" the other day when we invited a bunch of the neighborhood kids over to play and they all LOVED the little rocks. We paid $300 for a dump truck full, which is equivalent to 10 tons and it worked out perfectly (It would have cost around $1200 to fill with rubber mulch). It was a little messy at first (the gravel had a sandy/muddy film on it), but I went out there with a spray nozzle on our hose and a rake and washed a good party of it down before it started raining. The heavy rains also did a good job of cleaning up the half that I didn't get to, but since there wasn't any raking, the layer underneath was still dirty and the kids were a little dirty afterwards, but not bad. With the second wave of rain we just got over the weekend, I think it will be pretty clean. If you want to send me your email address, I can email you some pictures if you want.