This was our first cruise my wife and I took with the kids (3 and 4 year old) and the Norwegian Sun was a great choice. Five nights is perfect when traveling with small children, gives you just enough time to enjoy a perfect vacation keeping the kids happy. I have taken week long resort vacations with the kids and they always get cranky and home sick by the end of the week. We boarded the ship at 3pm on Tuesday, the check in process took about an hour, the lines were long and check-in clerks were slow. The clerk had trouble finding our reservation and had printed our cards wrong, so my card had my son's information which made ordering drinks at the bar fun. Once on the boat everything was great. If you are traveling with kids an II class cabin is a great value. We had a queen bed and a sofa bed that served as a queen bed. There was plenty of room and closet space. The bathroom was small but functional, just enough room to stand inside and shower the kids.
We went to the Kids Club to register the kids. They run programs free of charge from 9-12, 2-5, and 7-10 for days at sea, 7-10 only on port days. Sitting is available to 1AM for a small charge ($8 an hour for two kids). My kids loved the program, they attended every activity. The Kids Club was a life saver for us since the weather was cool, cloudy, and rainy on the two sailing days. The night program gave my wife an I a chance to dine in Sushi Ginza and the Steak House, they are well worth the cover charge.
The wait staff in the Seven Seas was great with the kids, they brought whatever they wanted, didn't matter what was on the menu. They were entertaining and patient. When it came to breakfast the waffle bar in Pacific Heights was the place to be. The view from the large windows is spectacular. It is not as noisy and busy as the buffets, but you can certainly make a plate at the full buffet and bring it over to Pacific Heights. My wife and the kids loved pasta bar for lunch (also in Pacific Heights). I preferred the sandwich bar in Las Ramblas, the bread is fresh, and all of the creations are excellent.