Getting around - I also recommend park hoping. AK is a good park, but you can really be done early. We were there just a few weeks ago and stopped for lunch for an hour and still got everything done pretty early. The busses can be annoying and sometimes you may have to wait for a bit at the end of the night, but you'll definitely save money on parking and renting a car.
After cruise transportation - Disney does offer transportation from the boat to resorts. Last time I checked, it was $70 per person. You can also arrange private transportation on your own. Depending on the size of your group, it may be cheaper to arrange private transportation through a sedan type service.
How busy - It could be pretty busy. It's spring break time, so that can get pretty busy. I also look at the operating hours. 9-7 is usually the slowest times, 9-12 or 1am is the absolute busiest (Jan. 1, July 4th, etc.). During April, most of it is 9-10 which is pretty busy. But with FP is should be manageable.
Also, what Disney ship are you on? If your doing the Fantasy, make sure you check out Robb's trip report he just posted!http://www.themeparkreview.com/forum/viewtopic.php?f=2&t=63856