Yes, I'm definitely prepared for rain, although surprisingly, April is one of the driest months of the year in Ketchikan. It's actually the 4th driest month, historically:
http://www.usclimatedata.com/climate...tates/usak0125
So I'm remotely optimistic we may only get some, rather than torrents, of rain. I also considered the weather when debating the JNU excursion. It's a tough airport to land at in perfect conditions, so I would be concerned about delays and getting socked in there (or in KTN) and have it really disrupt the trip.
I also thought about cars, and I've decided that if we stay in KTN the whole time, I'll likely rent a car for at least a day so we can explore the island. I know the bus system is good there, but I think it would be worth renting a car, even with the lack of extensive roads.
I also thought a good day excursion from KTN would be the ferry to Metlakatla and back, which I've always wanted to see. That also gets us on a boat, which is great since the touristy boats won't be running in April.