You need to consider this as 2 separate subsystesm:

1. A MIDI interface - there's plenty on the web about that

2. The drum-hit sensors.


I imagine that the output will look different depending on how hard you hit it? This is what you need to capture in your input stage.
I'd guess that it's the peak output that you want to measure?
You'll need to read the datasheets for your transducers, and probably also do some (many?) experimental measurements.



I think you'll probably find it much easier to at least start this way.
Once you've got it running, and experienced all the issues, you will be in a better position to judge.

I wouldn't be surprised if you needed some decent analogue front-end electronics for each sensor, at least...