We've sailed on HAL a number of times, including 4 times to Alaska (not using
DVC though). We also bring some silk long underwear (bought at REI), since one NEVER knows what the weather will be like in Alaska. It can be very warm and you'll be in shorts every day, or it can be on the 'nippy' side and the wind is cutting through your jeans. Since the silk is so thin it fits neatly under clothes and takes up NO space in a suitcse. We actually take 'the silks' about every time we travel. We rarely need them, but when we do, we are SO thankful we have them.
Particularly when at the glacier(s) we've spent the whole time outdoors. When it is on the cool side, it doesn't take much movement of the ship to create a chilly breeze. We'e found that keeping our heads covered (coat hood/hat) makes us much more comfortable outdoors for long periods.
HAL is a more 'traditional' cruise line. We've
rarely seen men on formal nights without a coat & tie. Usually it's been running about 50/50 dark suits and tuxes. DH used to take a dark suit, but lately he prefers renting a tux through
Cruiseline Formalwear as the tux is delivered to the cabin - less to pack. It is picked up from the cabin too.
If they have an 'informal' night, it is not 'casual'. It is 'not-formal'. Confused the heck out of us the first time. The daily program will say something along the lines that men are requested to wear jacket/sport coat, tie optional.
Have a GREAT time. The scenery is beautiful rain or shine.