I would recommend doing a sunset dinner cruise at least one night while in Dubai. It is a nice way to see the skyline at night, old and new. There is a lot of activity on the water, with all the cruises and water taxis, most of which have festive lights on them, so there is plenty to see. After a long day of sight seeing, it is a great way to relax while taking in the atmosphere.
We went with our kids (ages 9 and 7) and got there right on time (we left early and it was a good thing we did because it took us a bit to find the right boat - there are a lot of them!). I recommend going early to get the best seats, upstairs. We sat on the boat at the dock for a long while before we actually left. The buffet was nice, there was plenty for everyone. At one point a weird looking Micky came out and scared most of the kids (mine included) but then the tandori dancer came out and he was amazing!
It was a fun and relaxing way to end our day.