My advice is to decide on few things you really want to do and build your trip around that. Here are some unique things that would be worthy of building a trip around and ones I have done with my family.

Inside passage ferry ride or cruise (easy way to see lots of place in Alaska in comfort)
26 glacier cruise out of Whittier
Hike Mt. Alyeska - 7 glaciers bar has probably the best view of any bar in North America
Bear Viewing at Brooks camp or other bear viewing tours
fishing trip to bring some fish home
flightseeing Denali from Talkeenta
riding white pass railroad out of Skagway
homer

Alaska is a huge place and you can spend lots of time and money just getting from one area to the next. The campgrounds / hotels can be pretty busy during peak times so you will need to plan in advance.