You can do it either way. When you make your reservation, just add all of the people and their email addresses during the reservation process and you pay the amount shown at the end for everyone’s deposit.
Alternately, you can make your reservation for yourself or however many you want to pay for. Then when you receive your confirmation email containing your Group ID, you give that to the people that want to go as well. They can click the button that says “Join a Group” on the reservation page and complete the deposit on their own.