Everyone join the team matches! Team matches are what groups are all about.

Don't think you're letting down the side if you lose, nobody cares if you do - but it is soooooooooooooo satisfying to score a point for the team! The only way you can fail the team is by refusing to participate =)

They can also be a great chance to get a lesson from a much stronger player, or give one to a much weaker one, so don't worry about rating mismatches - I've given, and received, helpful unrated games as a direct result of participating in these events, so if you like that sort of thing, all the more reason...