For now it's probably ok but sand is too fine to function very well as grit and eventually they are going to need larger size chick grit, especially when they start eating anything besides their chick starter.
Chicks fed commercial chick starter do not need grit. The feed itself is much too fine to be of any concern. Once they are older and may be fed whole grains, grit is a good idea. Chickens that have access to sand, gravel and the ground normally find all the the grit they need themselves. It is during long periods of winter confinement when they need grit to process any coarser feeds you may provide.
Even Layer or Grower requires no added grit to digest.