Welcome to BYC! Please make yourself at home and we are here to help.
It really is your decision. I use shavings in my coop and I, personally, do not agree with the use of sand in the coop. But there are many sand users on here that will tell you that sand is the best bedding you could ever use in the coop. Sand is easier to clean and isn't as dusty. But your chickens will have to risk of crop impaction if they eat sand plus sand gets cold and hot easily.
I am one of those that worship sand!! Love it and will never go back to wood shavings! I use it in a COVERED run, in the coop AND even in the nest boxes!! Sand is easy to clean and maintain. It stays dry when wet, it absorbs all poop smells, keeps the flies away and the chickens love to scratch around in it. Works as grit as well. I find it wonderful to hose down in the summer time to keep the chickens incredibly cool...cool feet mean cool birds! I left shavings long ago and will never return. I do not recommend mixing sand and shavings however, one or the other.
Welcome to BYC. Glad you decided to join our flock. I prefer fine pea gravel or course river sand. If you do decide to use sand though, do not use beach sand or fine playground sand as chicks can mistake it for food and, as Mountain Peeps says, it can impact their crops. Use a very coarse sand with with smell pebbles in it or a fine pea gravel with very smooth, small stones, and there will be no danger of impacted crops. Please feel free to ask any other questions you may have. We are here to help in any way we can. Good luck with your flock.