It's up to you how many clothes you want to take, but it does sound like you're overpacking. Don't forget, there will be a laundry available if you need it.
For my first cruise, I didn't wear half of what I packed. Pared it down for my second cruise, didn't wear 1/4 of what I packed. Think I now know how to get it right for my next cruise!
Alaska cruises tend to be really casual (except during formal night of course), so take whatever you are comfortable in. If you like capris, go for it. I would think a sweatshirt would be a bit warm on the ship, and during a port excursion might become too warm and then what do you do? Think "layers": some T-shirts/short sleeved blouses, 1 or 2 sweaters, and a jacket. Then you can take items off or put them on as you need them. Be sure to bring raingear for ports of call. If you're out a lot on deck, you might want some light gloves and something to cover your ears--it can get pretty cold in the ocean wind.
Have a great trip!