If he's going to keep on top of the grass, don't worry about gravel then.
Just try and get some sturdy types of grass, because, IMO, no matter how well you keep on top of things the 'nicer' kinds of grass get easily worn down.
Coop, did you dig into the soil much for the sand pit? We need one of those for Middie, and I am thinking of doing it this summer. Problem is, we have red clay... ick. And it dried like.. well.. clay. So I shudder to think at the cost of the amount of sand I would probably need to use.