Hi dschweitzer, welcome to Cruise-Chat! Congratulations on your up-coming cruise! We've had quite a few members sail the Dream and reported back that the cruise was truly a dream. While Princess is my favorite, I've always enjoyed my Carnival cruises. Carnival is not as sedate as Princess or Celebrity or HAL, but their ships are clean, their crews are great, and their food is very good. You have to try the chocolate melting cake, at least once, it is so yummy!
You'll probably find more families with children on board, but then again, maybe not, since school will be in session.
Sorry, no midnight buffets, most lines have done away with them. They did do a chocolate buffet on our Valor cruise in May, it was during the day, though.
Each cruise line offers it's own uniqueness, so try not to compare one line to another. I know that sounds hard to do, but really it's easy. Who knows, Carnival might end up being your favorite line