[From back cover]:  Dawn and her brother, Jeff, are back in Stoneybrook for the summer.  And if that weren't enough excitement, the Baby-sitters have a school trip to Hawaii on the horizon.  The girls need to make a ton of money . . . in only a month!  In fact, the BSC has taken on so many jobs, they need help.  So when Jeff and the Pike triplets catch the baby-sitting bug and want to become BSC meebers, the club signs them up.  As Baby-sitters-in-Training, the boys are happy to eat junk food at the meetings and play around with the little kids.  But they don't want to change diapers, or miss Little League, or listen when Kristy calls meetings to order.  With help like this, wil the Baby-sitters ever get to Hawaii?