Hello,
I would suggest you wait until the chicks are a few weeks old. I typically find it important to use medicated chick feed for the first ten weeks before switching to an organic grower feed. At this time I begin to introduce grit, for a week or two, before providing scrap foods. This allows the birds to consume some of the grit to help with the digestion process.
It is extremely important that you remember to provide grit regularly. Most chickens, even those who are free range, don't get enough grit to properly digest their food. This can cause many problems as the bird is unable to retrieve the nutrients from their food and can even develop blockages.