What do you guys use as a substrate for your swing sets? My husband and I bought one that we are going to put together this spring, but can't decide what substrate we should use. I REALLY want the squishy rubber playground flooring type but not sure how difficult that would be to put in as far as having perfectly level ground, and all that. Plus hubs doesn't think it would hold up to the weed whacker. We(*I*) want long lasting durability, with little maintenance. I would like to stay away from regular mulch because one of our dogs LOVES eating sticks and I'd rather not give her a foreign body buffet. Rubber mulch is 100% out for the same reason but has more severity if ingested.