Hi Christopher!
You'll have a fabulous time celebrating with your little Princess at Walt Disney World!
There's no real way to know what fantastic offer Disney will offer next or what resorts or time periods it may cover. What I always recommend is to book the Resort & Package you're comfortable with in terms of price & date. That way, if a special offer doesn't become available for your travel dates, you'll still enjoy the great vacation you had planned & budgeted for.
Then, keep an eye on the Walt Disney World website's
'Special Offers' section as well as your local media like TV commercials and newspaper ads. If a new offer comes out, simply call (407) 939-7675 & mention that you have an existing reso & would like to switch to the "such & such" offer. The Cast Member will advise you of availability under the offer & can even help you compare to determine what's best for you! The offer may vary by resort level in terms of which properties have availability, what % discount is available or what 'free' add-ons such as dining are being offered.
For example, I was once booked at Disney's Port Orleans French Quarter Resort (which is a great choice!) when a 'Buy 4 nights Get 3 nights Free' offer came out. I called in, but that particular offer was sold out at POFQ. We couldn't receive a discount off our existing package price at a moderate resort, HOWEVER we ended up being able to upgrade to a Deluxe Resort under the new offer & our total package price remained almost exactly the same! We were thrilled!
I hope you'll visit again soon with any additional questions you may have.
Wishing you a Magical time as you plan your daughter's Walt Disney World birthday vacation Christopher!
Kirsten