I hadn't been tubing since childhood when we did the trip last year. I thought the whitewater was actually pretty easy, and there were smoother stretches in between that you could just float lazily through.
DB and I were talking about this today-- Since there is a combo trip, it could be possible to do a mix. Folks who want only flatwater could show up in the morning and do the Shenandoah. Then any folks who prefer whitewater could time their arrival for the lunch in between the two trips, so we could all hang out together as a group for a little while before the whitewater trip. And then there will be those of us who might just do both.
Or we could take a vote and go with the majority. There's plenty of time to figure it all out.