Although my favorite is Alpengeist, it should be a ride everyone likes, and there are some that have problems with Alpengeist and don't like Griffon... who doesn't like AC though? So, that's where my vote went.
I voted AC because Nessy wasn't there. Nessy is right near the front of the park and would be a good place to meet (Come on, who doens't like Nessy?)... (And then whoever wanted to could walk over to AC... )
Since it's only a day for passmembers, it probably won't be too crowded that we wouldn't be able to ride several together. I like AC. It's a good group ride, but I think Nessie is a great group ride, too. Maybe we could get someone to take our picture as we're waiting in the station or something.
I hate to say it, but Griffin would be the ride for all of us to get a group shot on. (Or most of us to get a group shot on... if half was one row behind the first. Personally, I always start my day at Busch Gardens with the Loch Ness and then move around the park in counter clockwise fashion... just a weird park ritual of mine. Still, any coaster is fine with me.