I give mine a bunch almost every day, and so far they havent shown much interest.
A few peck at it and some eat it, but I think thats just more from the competition in the brooder.
They are just about, if not 3 and 4 week old chicks, 28 total.
They love bits of grass tho, and go nutso scratching around for it all.
If you still have them in the brooder you will need to provide GRIT for them anytime you feed anything besides their chick starter feed.
Sand will work if you don't buy grit. TSC and most feedstores sells chick-sized grit from ManaPro brand and it's cheap enough. Just give em a tablespoon or so. It'll last forever
If the chicks are outside on the dirt they will probably get their own grit.