If your kid is sensitive and doesn't like the sand attempt introducing it a little at a time. Don't make too numerous demands. Deliver in a small box of sand and put a vehicle in it. Just have it available for the kid to see and go to on his own time schedule. Perform with the car and sand your self. Be sure to make fun seems that will peak his interest. Then allow him initiate touching the sane himself. Attempt a little nudge each session. When you go outside, have the sand (or gravel) box available but don't make demands.