My mother booked a room for me & my friends under her name , does she need to call ahead of time to inform them that we are the ones checking in or it doesn’t matter?

When booking a room, they usually ask for how many people, the ages of all who will be staying in the booked room, and then ask for those individual's names. You should find out from your mom if she had to give the names of all you guys. They also ask for identification at check in. I would get all the details from your mom first before trying to check in.

She should they may ask for the card used to reserve the room.