I've never given my chicks supplemental grit, figure they get what they need from the ground and from their feed. Call the maker of your chick feed to ask if they need extra grit, it may already be in there. I guess you could add a bit of chick grit to their feed if you wanted, if they seem to need it.
I like to pull clumps of grass/weeds for them to pick at, roots & dirt ball & all. I'll also provide a pan of dirt for them to dig in & take dust baths.
Often they're hesitant as a group to try a new food. Chickens are seldom trend-setters, instead they're usually fashion-followers. They wait until one brave bird gives it a try and doesn't drop dead, then they know it's safe to eat.
You can act like the Mama Hen, poke at the food with a finger and say "bok-bok-bok" to call them over, pick up & drop pinches of the food in front of them to encourage them.