Bluewahoo, HAL is great for the cruise part. On the formal nights, you can eat at the Lido deck restaurant, where you all can wear anything you want. In fact, I prefer eating there anyway, buffet-style, for all 3 meals. I like being able to choose what I want and exactly how much I want, and they have a good selection. Also, you get your meal HOT.
Not a fan of the main dining room,
. Went there ONCE the whole last cruise.
On the formal nights, your dad might want to wear slacks as opposed to shorts, whether eating or attending the floor show (and I highly recommend that you do--most of them are very entertaining). He'll be fine. The people I've met on HAL cruises aren't "stuffy" at all.
As to the landtour part, I went once with HAL and didn't like it. Too restrictive and the guide we had was hopeless. Better and cheaper to do your own thing. But if you're not sure what "your own thing" is, or prefer to have all the arrangements done for you, then by all means do the HAL landtour. Looks like a great itinerary.
One thing I would suggest--if you can fly up a day or 2 early, rent a car and explore Anchorage and environs. There is so much to see! If you're a glacier nut like me, you'll want to drive south to Whittier (can also go by train) and spend hours sitting beside glaciers listening to the crackling and gunshots as the glacier moves, and watch some fabulous calving! Also nearby is Portage glacier. You can look at the exibit and watch the movie, take the Ptarmigan boat to see the glacier, and hike for about an hour right up to Byron Glacier and see real live iceworms!
Have a great trip!