I just did something similar when I booked our bounce back for Aug. We had 1 room with 2 adults 1 child. I called to book 2 rooms for a total of 5 adults and 3 children. The CM just put one adult from our current trip as the primary occupant for each room. (However, If the other adult from the first trip was not traveling with you on the second trip you would only be able to book one room.)
It was not a problem for me to book both rooms in one phone call. I was also able to book a seperate bounce back stay in Dec. In total I had 2 rooms booked in my name (one for Aug, one for Dec) and 1 room booked in my DH name (for the other family joining us in Aug) So I guess you can book more than 1 bounce back room per person so long as they are for different dates.
Hope that is not too confusing. Good luck.