Ahoy Heather!
You are definitely in for a vacation of a lifetime on your Alaskan voyage this summer! I'm sure you can't wait to experience all that the Disney Wonder has to offer on this amazing journey!
As for clothing goes, I would recommend layers with a waterproof layer on the outside. Some type of comfortable waterproof shoe is going to be ideal since you will be in the snow. To save room in your suitcase, I suggest rolling your clothes. I have found this to help when packing for my past cruises because I'm able to get more in my suitcase and it doesn't seem to wrinkle.
If you haven't already, be sure to check out the
Alaskan video series, Cruise Mom Andi filmed while her family enjoyed the Wonder sailing. I'm sure you will find it very helpful while you prepare.
Thanks for visiting the Moms Panel with your question, Heather. If I can assist you further, please let me know!
Have a "Wonder"ful day!
Nancy