Day Cruises

Out of Whitier the 29 Glacier Cruise is a good day trip. From Seward Major Marine's Kenai Fords National Park Cruise turned up otters, humpback whales, puffins, porpoise, orcas, the Holgate Glacier, (which was actively calving), Aialik And Pedersen Glaciers, and that was just the first half of the day!
The Swiftwater Seafood Cafe has really good fish & chips in Whitier.
On the Seward Highway between Anchorage and Whittier is The Alaska Wildlife Conservation Center, which is definitely worth a visit.
Ditto on the tour coupon book. It will pay for itself the second time you use it.
My only other advice is to not wait, GO NEXT YEAR, we are!

Get a Tour Saver book for $100 and book the cruises in it. The book gets you 2 for 1 on what ever is in there, you will get your money back on the first cruise you take. I think we took nine different cruises.
There are good deals in the book available on line or in Carr's stores.
Don
here

We have not been to Whittier, but have taken several cruises with Kenai Fjords in Seward. I have not made resevations in the past, just stopped in when we got there, but I have not been there since 2008. Trips have been enjoyable. We also had a cruise on Major Marine and the weather shortened the trip. They gave us a partial refund since we did not get the full trip.

If you get to Valdez, I highly recommend Stan Stephens Cruises. They serve a lunch and afternoon snack on the longest cruise. Again I usually book after we get to town or call a day or two ahead once I know a weather forecast.

There are so many that you can wait unless you have your heart set on a certain tour. Half day, full day, wildlife cruise, glacier cruise, etc, they are all nice.