Love the Easter Eggers!
You can offer chick sized grit any time, but they don't actually need it until they start eating anything besides their chick starter.
I offer it when mine go to the coop section for chicks, because they start catching bugs, and get stuff in the litter and greens from the yard. They are about three weeks old then, or a bit younger.
If you start offering goodies sooner, get the grit to them sooner.
Mary