You need to do your homework and decide what you want to do first. I also suggest you have all your touring plans selected, THEN reserve. The problem that frequently happens is people get all excited over a particular tour, rush to book it, then keep getting more and more information- decide something else is a must do- either want to cancel what they booked- if independent- cancelation fees, or find they don't have the right time, etc etc etc.
So I suggest, you look over a shore excursion list- NARROW down your interests, DETERMINE your budget- this isn't the place to skimp in my opinion. List- perhaps your top 5 in each port, then continue to research. DO not hesistate to split up, tours are costly and there is no point in dragging someone along who isn't interested and no sense in missing out a great tour you want to take.
Myself, I never take ship tours and always book direct with the venders- there are many excellent ones in Alaska to consider.