I would take the nanny if you need her for the wedding. I don't trust anyone to watch our kids other than our nanny (e.g., no hotel sitter for us), and if that means that I would bring her out for 5 days, then so be it.
But, our nanny likes to travel with us, b/c it is an opportunity for her to make extra money. (e.g., we pay her for overtime (if applicable) and any time worked on weekends)
We also offer our nanny in the travel planning and offer her a day on either end of the trip if she wants time to explore.
It is just nice to have her with us so that we can go out to dinner, go for a run, and simply get some rare time with my husband.