I would not use it. crystalline silica is the byproduct of using real sand for industrial purposes. Its basically ultra find ground sand dust. Its pretty nasty and has osha regulations when using it. Odds are Bought cheap sand that was "recycled" from a plant that used the sand for molds etc.
It would be fine to use the sand outside, since there would be no build up, but indoors its pretty nasty when dry as an inhalation hazard. And since our little ones are prone to URI's...