Hi Suzanne,
Welcome to the Disney Parks Moms Panel and thank you for asking us a question!
The short answer to your first question is "yes... and no". From what I understand, all
special offers, including the "Stay Play and Dine" (i.e. Free Dining) promotion, are often limited to a certain number of reservations at each Walt Disney World Resort hotel. If you already have a Magic Your Way Vacation Package booked, you will have to cancel it and re-book it with a Resort that offers the Free Dining promotion. You may get lucky and be able to get a package that is identical to the one you had initially booked, but there is a chance that you may not. In that case, you'll have to choose a different room type/Resort if you want to take advantage of the special offer, or you'll have to stick with your original package (and cost).
If taking advantage of any special offers that may be released the moment they become available is important to you, I would recommend booking your vacation through an Authorized Disney Vacation Planner. Whenever I've worked with one, they were usually quite good at getting my vacation re-booked seamlessly so that I could take advantage of any special offers that may have been released during my vacation dates. I haven’t had as much luck making the switch when I’ve booked my vacations on my own.
As for adding
Disney’s Magical Express, you can absolutely add it later! In fact, I once added it the day before my arrival at Orlando International Airport! That being said, if using the luggage delivery service is important to you, you’ll definitely want to add it to your reservation as soon as possible so that you can get your luggage tags at home well before your departure date.
Have a Magical Day,
Lynne