Personally, I would not consider doing any cruise line but Disney with children. If I were unwilling or unable to pay the premium of a Disney cruise, I would skip that type of vacation until the children were in their teens (and then likely do Norwegian).
My grandson and I did a four-day Disney Bahamas cruise for his fourth birthday in 2005 and he loved it so much (when so much means had to pry his little hands off the luggage room's door frame to get him off the ship), we returned to do a seven-day Disney Eastern Caribbean cruise in for his seventh birthday in 2008. We then planned to do the tentatively scheduled ten-day Disney Mexican Riviera cruise out of California for his tenth birthday in 2011 but the bottom fell out the economy in between and it did not materialize.
So we decided to try something different and went with visiting Universal Studios for two days and then sailing on a seven-day Royal Caribbean Western Caribbean cruise. Royal Caribbean had the exact same itinerary as the Disney Western Caribbean cruise, it would be a whole new experience and it was a thousand dollars less. And it is not like we were/are huge Disney fans. We only sailed with Disney that first time because we were vacationing with huge Disney fans and they planned the trip.
Oh, what a mistake. Disney's child-geared entertainment and kids club were easily worth that extra thousand dollars. Not having the adult vibe, which included gambling, and the constant money-grubbing would have been worth even more.
I am taking my two granddaughters, ages 8 and 9, on a seven-day Disney Western Caribbean cruise in October. It is a little over twice the price of a comparable Royal Caribbean cruise (and a little under twice the price of a comparable Norwegian cruise). I only know that because I just looked it up. Even knowing that I have no regrets. Even if Royal Caribbean was a third of the price, I wouldn't have any regrets.
But if Disney was three times Royal Caribbean's price, we wouldn't be going.