This is where you need to have a full service travel agent working with you. They can ensure the party travels together as needed, and can return separately as needed. The individuals who do not return together with others will need to be on separate tickets.

Future.Travel handles these types of ticketing issues daily. Easy to online chat for support. The hotels are easily managed online (book it yourself) as you can have multiple hotel departure dates in one booking for different members of your group.