We sailed on HAL last summer (2007) and my 6 and 14 year old (then) loved it! Read the article on the homepage of the family section here on "Holland America gets family friendly" for more details.
HAL made HUGE changes to its youth and teen programming over the past few years since you cruised aboard. The youth program then only started at age 5 and now it starts at age 3. The new ships have great youth and teen facilities too. I think your family will really enjoy the Massdam or any other HAL ship.
And you can't beat the service -- thought the food was very good too!
Let me know what you decide.
Family Cruise Editor