Thanks to everyone for all the great input, I really appreciate it!
I left a message for the audiologist yesterday because I want to ask two things: (1) can we do the otoacoustic emissions test (as Katie M suggested - thanks for that!) instead of a sedated ABR, and (2) if it's determined that Finn actually does have hearing loss, what would they propose to do about it? Because if there isn't anything they would do about it anyway, then why do the test? Of course I haven't heard back from the audiologist.
Regardless, I've pretty much decided NOT to consent to the sedated ABR at this point. My understanding is that the hearing loss/impairment that is typically associated with Ds is due to chronic fluid in the inner ear. Finn now has tubes and no longer has fluid in his inner ears, as confirmed by the tympanometry test the other day. I really believe that he hears just fine, based on his behavior and response level at home, including the noticeable improvement he's shown since having the tubes placed. Plus, as someone pointed out to me, his tubes will fall out eventually and chances are he'll need to have more put in - they can do a sedated ABR then if they want to.
I'm sure sedation is generally safe, but like anything else, it carries risks, and I just feel like I have to be extra cautious with Finn. Actually, I think I'd have reservations about sedation for any of my kids unless it was completely necessary. It's that mama bear thing.
In other news, Finn has a summer cold now :( It's the first time he's been sick since he had the tubes placed. It will be interesting to see if he ends up with an ear infection.