If Port Canaveral remains closed for an extended time, I suppose
DCL would make arrangements for an alternative port. But there is a lot more than DCL using Port Canaveral so I expect disruption will be as minimal as possible because the port authority will get it back in shape to open as soon as possible. If there is significant damage to DCL’s terminal building, that could take a little longer but they would likely make arrangements to temporarily use another terminal at Port Canaveral.
As to excursion ports, some may need to be canceled. Some excursions may be canceled even if ships dock. The most likely scenario for a canceled port stop is an extra day at sea; occasionally they might change up the schedule but I wouldn’t expect that.
I think there are too many “ifs” for more detailed speculation at this point.