Hi. This will be my second cruise on the Dream. The first one (March, 2012, 5-night) was filled, but the ship didn't seem over-crowded. Wait until you see it! During the 2012 cruise, we sailed next to the Magic (or Wonder, if forget which) for a little while, and it seemed like we were next to a rowboat! I thought the Magic and Wonder were big, but the Dream is huge.
That said, I tend to be an "early riser" and get to things when they open, so didn't experience huge waits in line. The Aquaduck gets crowded, so you may wish to plan and get there early.
Also, the "artwork detective" activity is popular, so you may want to wait until later on in the cruise to try that out, or do it early or late in the day.
The Walt Disney Theater has a balcony that I enjoyed; it provided a great view of the stage, and there were fewer children up there. Being a Disney freak (as are others on this thread, I see

), I like kids, but I've got limits for fidgeting!
Hope this answers the questions above about crowds on board.