I would definitely avoid the edible substrates. Calcium sand gets impacted because most of the species put on sand are desert dwellers, and they don't drink enough to move the sand through their systems. So it clumps up in their intestines and solidifies.
I use washed playsand for my bearded dragon and uromastyx. When they get crickets, I put them in a tank that has just reptile carpet in it. Worms, I'll usually feed out of my hand or with tongs. Greens are in a dish, so there is little risk of them ingesting the sand.
If your leo's are hatchlings - juveniles, use a soft substrate like paper towels, newspaper, or reptile carpet. Once they're adult size, the sand shouldn't injure their skin.
I believe it's zoo-med that came out with a new clay/sand mix called "excavator". You mix water into it and can mold it into shapes, like hills and caves. Since it's more like the compacted earth they would encounter in the wild, it should be an excellent choice. I have yet to use it myself and don't know anyone who's tried it yet.
Hope that helps
