Scuba diving excursion on Mexican cruise

[Valencia Joe]

My wife has signed up for the scuba excursion in Cabo (she is bringing her diving gear with her). I am always worried about excursions being cancelled due to lack of attendance (that happened a couple of times to someone we met on the Mediterranean cruise last year). For those who have been on the Mexican cruise so far, do you know whether the scuba diving excursions were well attended?

With respect to a excursion being cancelled, does DCL let you know ahead of time (before the ship leaves), or do you find out on the ship the day you leave? If it is cancelled, how much of an effort does DCL make putting you in an excursion with the rest of your family (in this case, she is going scuba diving, while I take my daughters on the sea/land excursion)?

Thanks!