I seem to recall from somewhere that ants are repelled by mint. Try powdering dried mint and spread it in the sand.

Good luck

Ethan

I've used plain old soap and water in a spray bottle and sprayed the perimeter of my sandbox when I saw that they were around (I was more concerned with the "Pincher" bugs).
I only had to use it a few times and it seemed to work!!!
Hope this helps.

Cedarcide makes a bug repelant for pet beds that is basically cedar shavings. I have used it to keep fire ants out of my herb garden. It should be safe for the baby, even if he eats it (but I would check the label.) The shavings are soft, so no splinters.

Try corn meal around the sandbox. This remedy has been passed down in my family for years. I use it in my house and yard. What happens is that the ant brings it back to the colony eats it, drinks water, and then dies because the water swells the cornmeal in their stomachs. Sound bad but it really works!