If you are in fact going to be visiting BW for the entertainment, by all means use the parking lots. Even when I was dropped off by my ds in Dec there were plenty of parking places. Yes, you may have to walk quite a bit, but that's not the point. I think that most of the DVCers will have a problem with those who use a parking space at 8:00 am and then head off to the parks.
If for some reason you don't want to use the BW parking lots, you can always take a bus to MK then transfer to a BW bus. But that's kind of a pain. You can also take a cab.
But, I don't think there will be too many people that will have an issue if you want to park for a few hours that night while you are actually at the Boardwalk!!
Have a great time....Jellyrolls is terrific fun!!