Yes. During reservation process, you will be asked to specify if you are booking just for you or if you are booking for more than one person and the number of shares you intend to pay.
For each person besides you that you are paying for you will be asked to enter a valid email address and, if the person is not registered yet, to enter his name and surname. After that, you will be able to pay the total amount in a single instalment.
NB: Your participation is already counted, so you just need to provide details of the other members for whom you want to pay.