We are staying in the concierage level in the Polynesian for the first time in November.
A few of the things that concierage service offers is a lounge with food that is available throughout the day. The food choices vary with the time of day. There are things out for breakfast (muffins, bagels, etc.) including coffee and juice, snacks at lunchtime, appetizer type foods at dinner and desserts and different alcoholic beverages at night. Concierage also offers turndown service and robes in the room. I have also used them to pick up a couple of items to be in the room when we arrive. Concierage can also help you make your PSs, including those hard to get ones such as CRT. It is basically a service to pamper you.
I don't know how busy the hotels are when you are going. Probably not very. You could probably call to upgrade but you will pay the additional. If you are hoping to upgrade for free, I have heard that this just about never happens. Like I said, we have never been there but will be experiencing it in November and can hardly wait! Happy planning!