This is the coolest thing to go through.
I understand the wanting to plan things out as soon as the decision is made to book the cruise. I am the same way. But, just remember as well, that with the people doing B2B's as mentioned above, some people could be staying in Whittier even though it is a pretty remote town, or they could have people picking them up, so they all may not be trying to get an excursion or a transfer. Like said above, transfers are usually pretty easy to do. If it makes you feel more comfortable, call NCL and ask them to add the transfer on to your reservation. Then if an excursion does show up that you want to take instead, just cancel the transfer and book the excursion. That way, even if you are unable to book an excursion before it fills up, your trip to the airport would still be covered.