Yes, let him take chorus! 1) He wants to and he enjoys it 2) It sounds like he will likely end up with “deep” extracurriculars from it, which is nice for college apps 3) yes it’s great to have kids explore lots of options, but you can do this with outside interests, sports, classes, clubs (high school has lots of clubs) etc…and I’m guessing that many kids are a little less exploring by high school, and a little more into knowing what they want. 4) he might change his mind anyway, down the road.
Another poster asked where else you could explore things for free, and one idea is Boy Scouts! My DS explored many new things through Scouts…skiing, aviation, archery, rapelling, etc etc etc. Same for Girl Scouts.