Hi CountryGal, and welcome to cruise-chat.com.
I purchase airline tickets fairly frequently for both business and vacation travel. My advice is to buy them early. You'll be cruising during peak season, and the planes will fill quickly. Buying them early also enables you to choose seats that are together.
My guess is that these prices will not come down, but keep checking regardless. I believe that most airlines will give a credit.
I also suggest that you sign up for email notification of flight changes, and also check your reservation online from time to time. Airlines do change their schedules, and you'll need to call them if a change won't work for you (such as a flight too early in the day on the day you leave the cruise).