On other Tauck river cruises I recall a reference to some dinners being dress up a bit - jacket & tie. I don't see that in the booklet we received for our upcoming trip?
There may not be one. I noticed our cruise this summer the on board wait staff was dressed more casually than previous tours - knit polo shirts for day wear and just a shirt and tie at night. All four cruises we've taken had at least one dinner off ship but half were casual venues (an oompah band type castle on the Rhine and an outdoor dinner in provence) and half dressy (Vienna palace and a chateaux in Normandy). On board it's just the welcome reception and chefs signature dinner night that people make a special effort.
We were just on one of the Rhine cruises. Our guys wore sports coats for the Castle dinner and the gals all dressed up. Since they had the jackets, they wore them for the Chefs dinner and a couple more times without a tie. We saw all options...it’s a personal choice.