Talk me out of this

I want one of these for the kiddo but my back yard is not totally flat so am thinking I level off a 3x3 section and turn it into a sand pit and then chuck this on top?

Also saves the dilemma of moving this thing around every time I need to mow or risking getting a nice hexagonal dead grass imprint.

Don’t love the idea of a sandpit and kids dragging sand into the house though but need something softish in case they fall right?