Although Carnival does offer the 20's a number of clubs on their vessels they do tend to carry a lot of kids. With one passenger being 50 I highly recommend that you consider RCI Brilliance of the Seas -•16 bars, clubs and lounges that never have a cover, including The Colony Club featuring self-leveling pool tables, Scoreboard Sports Bar, and the Schooner Bar
Vision of the Seas Complete renovated last year •8 bars and lounges that never have a cover, including Some Enchanted Evening Lounge and the Champagne Bar
Princess Cruises Ruby Princess This means that Ruby Princess passengers will have plenty of places to enjoy good music, have a drink, or just have fun with new friends. The lounges range in decor from the ultra-modern Skywalkers Nightclub to the elegant Adagio Bar. The large Explorers Lounge and Club Fusion also serve as small theaters, with musical and variety entertainment
Celebrity Constellation is my favorite (5 nights thou) It offers 64 international craft beer selections including ales, lagers, lambics, ciders, wheat beers, seasonal and beer cocktails in addition to its already extensive collection of fine spirits. I feel this vessel is the "happy medium" with something classic for all.