jerseygirl1962. If you are like the rest of us, you will probably want to go back to Alaska for a 2nd or 3rd trip. So I suggest you just pick one or the other (they are both wonderful in their own respect) and you will have fabulous memories of your trip. Then you can do the other excursion on your next trip.
We have done both the walk on the glacier and the Misty Fjords floatplane (and also the George Inlet Crab Feast).
Hope these links work, but here is the Crab Feast and the Walk on the Glacier trip:
And here is the Float Plane (after the float plane we had them drop us at the Ketchikan City Park which is lovely and then walked back to Creek Street along Married Man's Trail - a must do in Ketchikan IMHO)
You are going to have a GREAT trip no matter which excursion you decide to take. ENJOY!