When mine was in a somewhat similar situation (wanted performance instrument major with double major in a non-music field, at a school with strong academics), this is how he approached it.
Most important and primary concern was the instrumental teacher. Your son should first make a list of EVERY school within the geographic area that he’s interested in (and that could be the entire country), that offers both a bassoon performance major and a good business/finance major. Next, he needs to research the teachers. There are online chat threads in which bassoonists will be discussing the teachers, the programs. He should ask his teachers at his precollege program for names and advice. He should find out what others say about the personality and teaching style of the bassoon instructors. He should listen to their recordings, because you tend to come out sounding like your teacher. He should also find out about the overall atmosphere at the music school of the colleges/U’s (friendly, supportive, hypercompetitive, high intensity), because he would be spending a lot of time there. Is it feasible to do a double major with business at those particular schools?
This should significantly narrow the field for him. Next step is to look at whether he is likely to get into the music school and the academic school. The music school will be entirely based upon his audition. Yes, being one of the two top players in All-State is nice, but honestly, unless your father is a Juilliard prof who also is a principal player in the NY Philharmonic, everything comes down to the audition. I know someone who had no prestigious background, no resume to speak of, who got into Juilliard because he had an amazing audition. And I knew someone who did have the above-mentioned pedigree, whose parent made a phone call when the student decided in July that yes, they DID want to go to Juilliard, and poof, she was in, without having even applied.
He should also seriously consider doing a pre-audition lesson with the potential teacher at any institutions which are feasible for him, and are at the top of his list. This is the final step in figuring out which teachers are a good match for him.
He will surely have to do an audition, of course will have to do an application to the main school, and may very well have to submit an additional application to the school of music. And yes, it is possible that his academics would not warrant admission to a school that would have taken him otherwise. But if he is truly spectacular at his audition, then it’s a question of being good enough for the academic admission, as opposed to also being fantastic academically. It’s not as if the process is totally disconnected - there would be some communication if his audition is wonderful, but his academics are in the “good enough to get in, just like 20,000 other applicants, but not good enough to guarantee an acceptance” range, it might be that the school of music would tell the business school or liberal arts college that they want him.
When my kid had gone through all of the criteria (they actually made a spreadsheet of all they were looking for to keep it straight), they wound up with only a handful of schools. And kid had initially been willing to go pretty much anywhere in the country. Those schools were U of Md, U Conn (in-state for us, plus their teacher for kid’s instrument was fantastic), Boston U, McGill, and I cannot recall the rest. They also threw in an application to a tippy-top where the kid had a letter from the conductor, and got in, and decided to go, even though they couldn’t major in performance or even study it, except outside of that school.
And then, of course, can you afford to send him to the schools that seem otherwise appropriate.
As you can see, you and kid need to network with other bassoon students who have recently gone through this. Search the music applications thread on here for bassoon, and you may get some useful advice. If it’s recent, you may be able to still message them. Have kid contact the senior bassoonists from All-State and his pre-college program, and ask them what they found out in their search. Check FB for a bassoonist thread, and look for bassoon forums online. A school that could be right in every other way is worthless to him, if they don’t have the right teacher for him.