I got that question today, and the answer is “just fine”. In fact, it is up and running, sort of doing what it is supposed to do. You see in the picture to the right what things looks like, and in this diagram, pump.pdf, what the circuit looks like.
All Arduino code is not written yet. I so far do only have one sensor and one relay managed by the code, but that works as it should.
If people have comments on the schematics, I do not mind getting ideas on how to improve it before I solder all together.