Depending upon the age of your kids, they may like the 7:45 to 8:15 "inbetween" shows more than the main theater show (except for Disney Dreams and Hercules and Golden Mickey's). They are close to the performers, they get to yell and scream at/with the performer and many kids get to help out in the show. These are some of the most enjoyable shows on the ship. The shows are great for the kids and will keep the adults entertained too (something Disney used to be very good at).
I would try to do both and have the kids come to both.
Disclaimer: If your children are under 7 they probably will not enjoy the welcome aboard and farewell variety shows (the main show) as much as the other main shows in the Walt Disney Theater.