You cannot let in 4 people to an attraction on your 4 Plusses, one person, one admission. You can use it 4 times in one day, hit 2 water parks, the Sports Complex and PI, a different person using it each time. In theory, park days and Plusses belong only to the purchaser of the ticket, but WDW has no way of knowing who bought what ticket. We freely use old Plusses all the time. One year the tickets were on our resort key-card in my wife's name as we used her credit card to buy them, and next year my daughter's fiancee used them to hit PI.
Bill From PA