Videomaker – Learn video production and editing, camera reviews › Forums › Technique › Miscellaneous Techniques › Band at a gig › Agree audio is key.
I agree with Rocky's recommendations about the two cameras but you can mount the second camera on a tripod and pan or tilt between shots. Hand holding well is a difficult skill to learn.
For sound I recommend an external 4 channel recorder like a Zoom H4n. The last gig I shot the band used 3 separate amps rather than one and I didn't have the cables to get feeds for each. I will be adding these to the kit soon. The sound of the vocals got lost in the sound from the nearer speaker that had the instrumentals. The more you can learn about the band's setup ahead of time the better.