we did alaska (inside passage to and from vancouver) last august with our then 7 and 10 year olds. we did holland america (hal) because we are disney vacation club members and they are the only line (other than disney) that you can use points for. i would NOT reccommend hal after anyone has done a
disney cruise (you will compare everything and find they fall far below in all categories) and esp. would encourage anyone with kids to avoid it like the plague!
the kid's club was a joke-it was only open for a few hours in the afternoon and a few hours at night (which conflicted with the end of the early dinner seating and the end of the late dinner seating:we only ate in the dining room one night because of the hours). they had a space smaller than a disney stateroom dedicated to the entire "kids program", and while they did have a naturalist speak to the kids one afternoon, the majority of the time it was coloring, board games or videos. if your child does not want to do the set activity for the session they offer no other options and the child must leave. we saw 2 computers in the room and asked if these were available to the kids-we were told "only during computer time" (found out later that the kids stood in line to take 10 minute turns). hal has no pager system for the parents, so if you have a child that tends to get bored (as my son did very quickly) you are told to call the club every 30 minutes from wherever you are onboard or risk "permanant exculsion". we also found the kid's staff to be very unfriendly.
we spoke to the director of the kids club (who happened to be a former disney cruiseline kids program director) and asked what the deal was. he openly admitted that hal was making big efforts to market themselves as family friendly but was not putting any effort (or $$$) into it. he said that hal had hired prior disney staff (esp. in the kid's programs) but most leave as soon as their contracts are up to return to disney, that the staff he ends up with in the kid's programs "never hired on to work with kids" and end up there in addition to their "real on board job".
I would highly reccommend an alaskan cruise, i have never seen anything like the scenery and my kids loved everything we saw. i would however, look into carnival-we pulled into dock with them and i spoke with some of the passenger that had kids my age to see what their experience was like. they agreed that alaskan cruises are def. geared to older passengers (hey-i'm in my early 40's and we were "the kids" on our trip) but said that carnival did a very good job with the kid's programming on the trip. they said it was not the "party ship" atmosphere most people associate with a carnival cruise, more laid back and quiet-but there were things to keep the kids engaged and happy.
p.s. i've read on other boards that hal's service has continued to decline since the 5/04 introduction of "automatic tipping" (the line determines the amount of tipping you should do and automaticly posts it to your room account-if you request to decrease it, eliminate it, or exclude someone: you get multiple phone

calls and/or a personal visit to your cabin from the staff to inquire why).