I have a 12X18 sq ft piece of land to bid on that needs to be leveled for a play structure that will be put in. I need a little help with this. Would you use top soil to fill in the holes that are in the lawn to level all this out or would you use a topsoil/sand mix to make sure the ground is firm and stable for the play structure? Or would you use something different all together? After fill in all the holes and going over the small piece of land I would be rolling it out to level it as well. Any help on this would be great. Thanks!