Congrats on planning your first Alaska cruise. I've never traveled with young kids, so can't give you specifics related to them, but here are my thoughts given that you will not be choosing an adult-only line:

Cruise Line: We thought that for a big ship, Celebrity did a good job.

Side of ship: If you can get it shore-facing, that is a plus. I would not choose a cruise just based upon availability of shore-facing suites. Often, the shore is quite a distance without recognizable features.

Time of year: If you think snow on ground is scenic, go for the earliest cruise available. Otherwise, weather is variable and unpredictable. We have had some of the best weather in September, a time when we were told it is too "iffy."

Itinerary: Yep-Glacier Bay is the way to go, if you can. If not, you will return to Alaska someday and see it.

If you start to settle on a particular cruiseline, lots of people here can give you better information. Also, check out Cruisecritic.com for reviews and helpful threads for each cruiseline and each ship and each voyage.

Bon voyage!