Can't offer any suggestions on a seat, but I can say that'll be a great ride.
I used to live in Ft Lauderdale ('bout 20 years ago).
Also in Davie FL for a bit. They had one of the few McDonalds with a corral for horses !!
The Blue Ridge Prkwy is AWESOME !! Just watch some of the twisties !!! The deer around there ARE NOT very afraid of vehicles, and will just stand there, in the middle of the road, even as ya drive by them.
Enjoy the ride, and if ya can't find a seat in time, maybe consider a sheepskin cover for now.
AKA: Tim & 'The Adventure Cycle' VROC #24567, NEVROC, SteelCity VROC
"When life throws you curves,
Aim for the apex."