Re. electric drums, I would take an output from each drum just like if you were micing a regular set.
If you are short on inputs you can group them into a few inputs such as: kick, toms,cymbals,snare.
You will need some degree of control better than 1 total kit input. Not only for your main feeds but monitors will become a huge issue with electric drums. Since the other players on stage will no longer have a acoustic kick and snare they can hear, it will be necessary to put drums in their monitors or to a central monitor on stage.
As a drummer that does on occasion use Roland V-drums I find if I can't monitor the drums right on stage, I would prefer not even to try to use them live. I run a keyboard amp on stage for just the drums ( Roland k-500)
So I can be sure they are heard by everyone.
Another problem with electric drums on stage is that your drummer will most certainly have a few programs he/she likes to use for different sounds. If these sounds are programmed with different volumes on the instruments, every time they switch programs you will need to reset your faders so the mix will be proper.
Once they set up their programs, spend a lot of time normalizing each one so they all have the same basic volume on key elements like kick, snare, cymbals, and toms.
