The only reason I think December 8th might be better, is a lot of companies have Christmas parties on the last 2 Saturdays before Christmas. It makes no difference to me, but I just think more people could participate that weekend.

As for the Cowlitz, I have never been there, but either river works for me. If the Cowlitz is the chosen river, how is it to row for those who have never been on it? I know the Lewis is an easy row for anyone who has not floated it.