It was posted at least a month ago on a thread here somewhere that excursions for any cruise could be booked immediately. I booked all of my excursions for September’s Silver Muse cruises and November’s Dawn cruises back then. I don’t remember now who gave us the heads up, but thank you. Being able to book excursions immediately after paying your deposit is now a welcome benefit for booking early.
This is where a TA is useful. If there is an emergency at home, they contact your TA who will then contact you.
But as stated above, all that contact information will come to you in your documentation. After all, you don't need to be contacted through the ship before you board!