Welcome and congrats on the wonderful Christmas gift! My sons got me a trailer hitch put on my pickup and I LOVE IT. Country gals get good stuff!
I'm over in Walton County...Hiya!
As far as grit, since I keep the new chicks in a bin in my workroom, they get a dish of fine grit, either they have to pick the fines out of the general sized grit, or I pick up a bird grit box from the pet store, like for budgies. I've read no extra calcium until they are close to laying age.
from Washington State glad you joined us!
What a great x-mas gift! You can give grit at any time, grit helps break there food up. Oyster shells have ready when they start laying it gives them extra calcium they might need, just put in a bowl for free choice.