I have been to Alaska, and I highly recommend it, as long as you are not expecting the same experience as you get in the Caribbean. We had warm-ish weather in late August, but not sunbathing warm. 60s - 70s. The pools were pretty much empty.
That said, if you are into wildlife and nature, it doesn't get better than Alaska. We took the train with the glass sides from Anchorage down to the port, and it was some of the most beautiful scenery I have ever experienced. We saw moose, black bear, eagles. On board the ship we had a wildlife expert who would point out what you could see from the deck. It seemed like every day there were whales, orcas, dolphins, etc. alongside the ship somewhere. The glaciers are something everybody should see once.
Our son was 3 when we went, and he did not do well with the time changes. We flew from the east coast, so it was a 5 hour difference. It seemed like as soon as he adjusted to the time change, it was time to fly back home!
Landing in Anchorage at 10:30 PM in broad daylight was surreal. We were in the cab going to the hotel at 11:30 watching the sunset.