Disney cruisewear is much more casual than other lines. You can wear whatever you'd like on the ship/main dining room except swim suits. Having said that depending upon the length of the cruise there is a formal and a semi formal night...it's still optional and you'll see people in casual clothes, church clothes, sundresses, formal dresses. Wear what makes you happy. Palo (the upcharge restaurant) does have a dress code, basically any dress/pantsuit should be fine.
For true learning opportunities, that's more limited to Alaska and Panama canal cruises although there were a few sessions on my Baltic Sea cruise, more related to shopping, but I learned a bit about amber and matrioshka dolls.
There are cooking classes (watching a chef cook a recipe and getting to taste a sample), towel and napkin folding lessons, character drawing classes, crafts (a lot of 3D paper crafts), trivia, game shows, bingo (you pay to play), movies, theater shows, various entertainment (magician/comedian, etc), live music in lounges, etc. You can also pay for alcohol tasting classes and spa sessions. The gym is free, some gym classes have a charge, others are free and there is a walking/jogging track that goes around the ship on deck 4. Dancing classes tend to be limited to the longer cruises like transatlantic and Panama canal. They also have the art of the theme show tour which is different from the first day walking tour. The art tour tells you all about the theming of the ship, we really enjoyed it!