If you want to get them a large quantity of diapers and they don't have a preferred brand, I'd get a couple of different brands. Babies react differently and diapers fit every baby different! Get a middle size pack of Pampers, Huggies, Luvs, a store brand, etc.
Also HIGHLY recommend getting size 1 or 2, not just newborn size! We've used Costco wipes and are very happy with them. Our go to for diapers is Sam's club. But Up&Up (Target's brand) are really good options for diapers too.