How does one dress for a range of unknown weather and how dressy do we need?
You can dress as causal as you can. Make comfortable shoes your most important item and then be able to add and subtract a sweater and a light to medium jacket as needed. If you will have a Yangtze River cruise, men should at least bring a tie and a shirt (Suit is not necessary). For ladies, you can dress as beautiful as you wish because you will have a welcome cocktail party and a farewell banquet on boat.