Everything's going to be just fine, I'm sure you will all have a blast!
No, I haven't cruised up there, so I can't give you any advice on the ship or the ports, but I can remind you that "you'll be cruising"!
And try not to get worked up and worry about others having a good time. Their enjoyment will take care of itself. And as for gramma, she'll probably have the most fun of all! lol Take care of you and your husband, it'll be fine...