Hi Kelli,
I have a couple of suggestions for you.
First, do not wait for a discount to become available before booking your room. I've made this mistake several times and then was surprised to see that no availability was left at the resort in which my family wanted to stay.
Now, I book the room at the regular rate and then when an offer becomes available, I call to have my current reservation modified to the new
special offer.
Next, for free Disney Dining offers, you only need to check in during the dates covered by the offer. If your arrival date falls within the select dates, then you'll be extended the offer for all of your vacation!
And finally, you can certainly change offers if a better option becomes available. Just pay close attention to the terms and conditions of your vacation package.
I hope this info helps!