We went the Christmas/New Years 07/08. It was AMAZING. We had a wonderful time. We didn't cruise, but stayed on one island (San Cristobal)
The camera is a must bring, and if you can get an underwater housing, that is even cooler. Here's our pictures:
http://www.adamlyon.com/gallery/v/Vacations/2007-12_ecuador/
Although we didn't have anyone under the age of 18 with us, we all felt watching some tv shows about the Galapagos helped us understand what we were going into. I know there's a great
National Geographic Channel one. If you can get that on DVD, I bet your kids would really like it.
Gosh, I don't know if I can give any other specific tips, since the cruise is not what we did. But if you're spending anytime in Quito, I can give you some ideas there.