It's probably overkill for this purpose, but BluePhoneElite 2 might do what you want. It's a program that allows you to operate your cell phone from your Mac. It's got a lot of features for people that use their phone a lot (think salespeople), call logging, etc.
But this feature is relevant:
"Use your computer's microphone and speakers like a Bluetooth hands-free device!"
Not sure if it supports A2DP sink, though. I think they're talking about HSP (Headset Profile), which is mono.
This might be sufficient for your needs. Presumably you're more interested in the commentary than in accurate crowd sounds. 😉