Welcome to the club!
Growing up in the early 70's, the neighbors would always call the police on me and my never ending series of bandmates. After a while we got the know the cops on our beat pretty well. They would come in and my mom would make them coffee and after a while they were pretty cool about it. They said they had to show up because of the complaint, but they just asked us to turn down and went on their way. I was playing mainly Sunn and Fender amps back then.
I think one poor woman who lived next door had to go to a shrink because she just couldn't stanbd the noise. My parents were VERY cool to support my music.
Your son's Marshall will no doubt become a favorite of your neighbors in short order......
Good luck

Some much gear... So little time...
Don't you know that it's a fool that plays it cool... Paul McCartney