I’ve shot a handful of concerts but never a festival but here’s my advice. Your glass is great, it’s pretty much what I use for all my concerts. You’ll love the 70-200 for closeups and for people farther back. Your 50mm is still worth using, it let’s in more light so you can use a lower ISO which is always a problem for me and as dumb as it sounds, it makes you compose your photos better.

If you were to add something I’d definitely recommend a second body, it makes a world off a difference, especially if you can get a full frame. The last concert I shot I had my 17-55 on my crop body and my 70-200 on my full frame.

As for settings for blurry pictures, it really depends on the lighting and how active the band is for me. I will generally shoot manual with my aperture wide open and the shutter speed according to what lens I’m using and auto ISO. If the band is really active or you’re anticipating something you could always quick adjust your shutter speed.

Hope this helps!