I don't think it's too early to start, but I would just move slowly. Focus on fundamentals, sight-reading, etc., and maybe pass out 1 tune and start reading a little the last 10 minutes of class. If you do that over the next few weeks, you would have a nice start and plenty of time to dig in and rehearse your pieces hard in the month prior to your concert.

Also, think about the difficulty of literature you would like to play. If you want to play something that is fairly challenging (a level up than what you expect them to play for example), now would be a good time to start introducing it to them without our passing out 3 or 4 tunes and just rehearsing hard for 10 weeks.