I want to avoid is just sort of passing on your mix to your team member and having them do a large chunk of work on it. Having your team members play parts for you is certainly allowed. They can also help with production advice and instruction.
The main thing to remember is that if it's your turn to be the remixer for your team, it's your show. You're the primary arranger; you're the primary artist. You're in charge of coming up with the main concept of your remix and executing that concept. Your team members are there to support and help you, but they shouldn't be doing the work for you.
I also want to stress that you cannot collaborate with people who are not on your team. This obviously means no collaborations with other teams, but it also includes people not involved with the competition, i.e. you can't get your sister to play drums for you, and you can't get your boyfriend to throw some vocals down either.
Hope that clears things up.