Hi Tawn,
First, let me tell you the Pop Century is my family's favorite value resort. We stayed there shortly after it opened in 2003, and we've visited at least twice a year since then. I think you will enjoy your stay there.
And yes, if free dining or another special offer becomes available, you will be able to contact Disney and modify your reservation. Please remember that, in the past, the free dining offer has only been available with full-price rooms. So you will have to do a little math to see whether free dining really will save you money. You may find that taking advantage of a room discount saves you more. It all depends on your family size and dining preferences.
My suggestion would be to go on and book the best resort deal you can find right now that fits within your budget. Then keep an eye on the
Disney website for any other special offers that come available.
I hope that helps. Please let me know if I can answer any other questions as you plan your visit. Enjoy!
Wilma