There are several issues including ages of kids and what time zone you are used to. If you are on the east coast doing an east coast cruise with little kids, you'll probably function better with early seating. Remember that if you don't get early when you make ressies, you can always go to "Dining Changes" after you board and make your request again. There is no guarantee, but they do try to meet requests.
If you are a west coast family travelling with little ones, you might find early seating to be too early!
DD is now a teen. That said, we really like the late seating. If you get hungry earlier, you can always grab a snack on deck 9 or get a cheese plate from room service. One of the reasons we enjoy it is that there are many fewer young children acting out at late seating (yes, mine was young once, but it's nice not to listen to it at this stage in my life....and mine was never allowed to exhibit the behavior that some children show!) Late seating is 8:30. You can eat and be out by 9:45 without rushing (if your server is anything other than totally slow). Sure, you can linger much longer if you'd like.....
If you are stuck with late and it is just too late for the kids, feed them earlier on deck 9 (either on your own or with the programming group), and then put them in the programming while you enjoy dinner. Some of the best kid programs occur during the late seating dinner, and in the club, the kids can sleep if they want to.