Kids love playing in sand, and what's shown here is the perfect way to allow them this opportunity in a safe way. Keep the sand contained in an area that can be well covered when not in use, so local pets, birds and feral animals aren't able to access it for depositing their pathogenic waste. It's also important to know about potential liabilities with playground sand.

Make sure that silica is what's used, which is different from construction-grade sand. Silica is comprised of little round particulates, whereas the average sand used for other purposes can be jagged and rough when viewed through magnification. Obviously the latter can be very abrasive, and silica is not.

Silica is what's used for making glass. It's also used in sandblasting, due to its uniform round particle size that can be more easily controlled through a pressurized sprayer for sandblasting (etching glass or abrading surfaces). The insurance industry doesn't like silica, because tiny airborne pulverized silica dust particulates can be inhaled into the lungs, causing silicosis, severely damaging the tissue and limiting oxygen processing, without any way to stop the continuing deterioration or reverse it, typically resulting in death. None of this is going on in a sandbox, yet it's worth knowing about if anyone brings it up. 

The bottom line here is make sure you have a secure cover to place over your sandbox whenever it is not in use, that is study enough to keep out the local bugs, pests, rodents, critters, pets and feral animals.