It's free for members only at the DVC resorts (BW, BC, WL), you don't have to be staying on points or even staying at WDW to get it, just show your member card.
I always valet when we arrive, it's easier to just have them take the luggage and the car and go right in to check-in. After that, we usually self-park. Sometimes that can be a challenge at BWV, especially in the evening, you may have to drive around to find a space. Valet was convenient last year when we had some heavy rain, we just valeted the car instead of walking in the rain.