Good news then
The type of concert was not originally defined, so I'm now guessing, that what your describing as community music festival, will have a much more relaxed policy on both access and shooting rights. This could present a great opportunity to be able to capture some superb images.
I would suggest at 30 rows or less, your 85 & 135 should be ideal for the job and maybe if you can borrow a fast 200, for tighter head & shoulder shots.
The 50 will work well if you right up near the stage or performing area, but when you be at that point you may wish to go a lot wider (I notice you have 15mm in your kit list).
You may may need to crank up the ISO a bit, subject to lighting conditions of the event and the level of movement of the performers.
Above all, enjoy both the experience and the show.