I just wanted to hop in and say that if you really want to use sand, try getting some play sand from a hardware store. It's cheaper, I think, and much less dangerous that calci-sand, or any other man made chemical sands. (Pretty much anything you find in a pet store).
Or, of course, you can avoid it altogether.
I LOVE the rock shelf you've got there. Simple and clever. And it really makes the cage look super clean.
Edit: Oh wait, *baby* geckos? Yeah, ditch the sand altogether at least until they're older. I went back up and re-read your post and that caught my eye. They are much more at risk for impaction and having respiratory problems from the dust. Best to keep them on something like tile or paper towels.