I have not gone on this particular excursion but we do go on 3-5 dolphin/whale watching tours per year in NJ and DE. The best I can say about any tour of this type is nature is unpredictable. You are not going out to view tamed/trained animals in a penned in area, so there is the chance you may not see anything or you could be so lucky that you catch sight of several animals of all species. If the kids and grandma go in with the expectation of relaxing on a different type of cruise rather than feeling that it's not worth unless there is a guarantee of some sort of animal sighting they should be OK.
There are times of the year where it is more likely you'll have a chance to glimpse certain wildlife than others ...
Whales: between July and September
Dolphins: between mid May and mid September
Seal: are pretty much there year round but surface more to play in open water during the summer months
I do remember hearing a PA announcement while at dinner, my last time cruising up there, about dolphins being sighted leading the ship out of port.
This post provided by Maryred, not Alanred.
Pending 2012 Carnival ??????
July 2011 Carnival Glory
October 2010 Carnival Pride
2003 RCCL Sovereign Of the Seas, 1993 vacation 2 Premier Oceanic , 1993 vacation 1 Premier Oceanic, 1990 Premier Atlantic - honeymoon - 1st cruise & Disney vacation