It may actually be 26, not that that helps much!
We bought this set:
http://www.bjs.com/adventure-playset...product.124951
We came up with the tonnage based on the following:
With a 6 ft perimeter, it would be 30x30, but we're going to cut it back a bit on the side of the swings, a little on the front and back to make it 24x28=672 sq ft. Divide by 27 for sq yds=24.88=34.8 tons at 12" thick, 17.5ish at 6", 26.15 at 9" thick. So if we went by the strictest recs, we should technically have even more (46.6 tons!), but I'm comfortable with the compromise.
We have a long sloping driveway, and they're bringing the gravel in on a semi which could actually fit, but would probably crack it, so they're going to dump it on the street. Luckily, the side of our yard is still just clay (new construction), so no worries about tearing up the yard.
It's $125 to rent a Bobcat for 1/2 a day, so I'm thinking that's probably the way to go.