These are business acquaintances, just like a resume, you should impress.
Bring a 6" Chiappa Rhino.
It's doesn't look like a carry piece so you give nothing away.
It is a blend of progressive technology applied to an old school wheel gun.
It is neither new nor old, the caliber is powerful yet not over-the-top.
It says "I can get the job done".
It is easy to shoot and unique all at the same time.
I just talked myself into buying one
One of my good buddies really wants one of these for similar reasons. He likes the new twist on an old concept.
Anyways, I'd bring some milsurp and a handgun. Even if they don't collect milsurp themselves, lots of people admire a nice Garand or 1903 Springfield. They can also start up some pretty good conversations. A semi-auto handgun can be pretty generic. I can't imagine most people getting upset if you were to bring a pretty vanilla handgun.
If they weren't work companions, I'd be more okay with pulling out the AR's, SCAR's, AK's and the likes, but I'd go for a bit more conservative stuff given the situation.