JMO, but you cant go wrong with any excursion that you can afford and interest you for Alaska. Everything is a must see or must do.
Since you are with a large group, split up and do whatever anyone wants.
You will save a few pennies by booking privately. Many reputable companies are available. The one advantage of booking with the cruise line is if you run into trouble, flat tire, traffic delays and are late to the ship, the ship will wait for you. If not start waving and get that credit card out.
Clothes....layers, layers, layers. Mother Nature is more unpredictable in Alaska than she is back home. I bought windpants at Walmart and wore them during the day. Very light weight for packing. Sorry fashion police but I wore a few things twice.
I went in August and came home with a sun tan. My parents went the exact same week a few years prior and my dad had to buy a winter coat.
I bought t-shirts there and worn them. Why pack them since I did plan to buy. I also bought my sweatshirt there too.
