As said the water-level is USUALLY pretty consistent. They usually give the expected water on weekends, it's just usually for not the full release (I.e. This past Sunday was 825 or so but only ran from 10:30-1:30) putting in at 11 was more than enough to push rafts down just not hours to play.
As far as carpooling I'll be up there the night before (guiding on Saturday) so I'm just going o stay up there. I can shuttle but im not planning on going up Sunday am...let me know