Children and pets should avoid playing in grass when fertilizers or any other chemicals are applied for the maintenance of grass. It's generally recommended that kids and pets should wait for about 24-72 hours after a fertilizer application. Also the lawn should be watered well before the kids go back to playing in the grass. Weed control products, pest control products pose no risk to children or pets once dry. Even organic fertilizers have the same illness effect on pets/kids as consuming large amounts of synthetic fertilizer. Hence, keeping an eye on children and pets while they play on a treated lawn, is unavoidable.