I'm going to be working on something similar. Any tips on sensing the ball going through the goal? I was thinking and ultrasonic sensor and an arduino.
The one I did was just a motion sensor that I put facing the ball drop (I have a Cyclone II so the balls return to the middle). It would be slightly harder if you had the end goals only because you have to make sure your hand doesn't set off the sensor.
The stuff I did worked 'ok' but there was definitely some flakiness with using two sensors instead of one. I think that possibly there wasn't enough power to drive everything.
Overall, I would want:
Something more stable in regards to sensors
Something with better sound quality
something that allows for more clips
However, without doing this initial thing, I probably wouldn't be prepared for step two.