Birds only need grit if you are feeding them treats other than their normal feed. You will probably want to wait until they are a bit older to start feeding them additional treats. So no, at this stage your little ones do not need any grit.
Enjoy them while they are young - they grow up very, very quickly.
I lost 2 baby chicks and I'm wondering if it was because I started feeding them veggies to soon without grit, broke my heart. We put a corn on the cob in and they seemed to love it. Perhaps it's normal to lose a couple when getting them shipped as day olds, but did not make it any easier. They are on chick starter and vit. water. Also do 2 week old chicks need light at night if it is warm enough for them and they are not crowding? Thank you so much I'm grew up with chickens and am starting up again after 20 years.