The upgrade is the cost difference between the quick service and the table service plan which I think is approx $20/adult per night. It's considerably less for a child. There are a couple of websites that provide detailed reviews of this. Tom Bricker's disneytouristblog being one.
Don't forget that you also need to tip on those TS meals. It's been years since I went during Free Dining and I did upgrade but it was my niece who was under 9 and myself (added approx. $10 each TS in tips). If free dining is offered during our trip this year, I won't be upgrading as she is now considered an adult. If I feel like it I can always add in a TS or two.
I believe In the past the grand floridian, poly and any 3 bedroom villas have not been included. So you might be ok unless you booked renting dvc points and then you won't be able to take advantage of it if it is offered.
I'm not familiar with dvc points. What are these ?
I was having the same concern/issue when I attempted to book for my fall trip. I called Disney and they confirmed that there is technically rooms available however they aren't all available for booking for various dates due to inventory management systems. Sometimes they hold rooms to make sure they don't overbook based on forecasting or up coming offers. I suspect that they are holding onto a few rooms in different category types in advance on the new offers being released. Their advice to me was to keep looking as room availability and release happens/changes daily. Good luck!
