Norrina, can I just say I LOVE how musical your family seems to be?
Although my sibs and I all had piano lessons, my parents were both non-musical and only one of my brothers was allowed non-piano music lessons. I realize it's a difficult situation you are in right now with the bussing rules, but giving DSS access to violin, trombone and drums, not to mention quiet guitar music at night...this is something that's going to pay back in a good way later in his life. Maybe he'll have a job in music, maybe not, but the discipline, concentration and finger strength will stick with him in future endeavors.
As for the bus situation, seeing how you are dealing with it (calling authorities, waiting, keeping calm, searching for answers for everyone and not just yourselves) is teaching him a different sort of discipline, to wait until answers are obtained instead of turning to Step 1: Freaking Out. Kudos to you!
All my family except me. :-( My youngest brother ended up with the most skill, he started violin at 4, went to a boarding HS for the arts, and plays in a small professional orchestra now. My middle brother took piano as a child, but never really excelled at it. My dad used to play violin (I haven't heard him play since now 22 y.o. DYB was practicing as a young boy), and worked in a violin shop when I was a baby. My mom used to play guitar and apparently was in a band as a teenager, but she sold her guitar when I was a child, and I don't think I ever heard her play. Then DF taught himself guitar when he was about 12, and his dream is to one day have a music room in the house. And DSS has taken violin and now trombone, he plays around on the drums, and over the summer DF taught him a little guitar (which he picked up right away and played a Guitar Hero song, but I don't remember which one now). He's a little sponge, he can hear a song once and sing it word for word the next time he hears it.
I never got music lessons as a child, largely because the money wasn't there (my middle brother is 5 1/2 years younger, and my youngest brother 11 years, so my parents were in a better place financially as they grew up), but possibly also because I didn't show the same potential. I found that playing Guitar Hero now has really helped my rhythmicity though, and understanding how the parts of music go together. I think I would have had a different understanding of the world around me as a whole if I had had musical training as a child, and I'm really glad that DSS is getting that opportunity.
I actually tend towards being a bit of a hothead, so I'm working very hard at staying calm and polite and going through all the proper channels here. I think it is actually helping that while this is a nuisance for us, it isn't meaning DSS can't continue playing, so I really am moving forward for the benefit of the other children, and that makes it less personal.