I can see being turned away due to full parking during holidays, Thanksgiving, Christmas, New Years if the lots are full. And who would want to drive in that crazy traffic anyway. Always best to take wdw transportation during those times.
But normally, you wouldn't have a problem parking at a resort for an ADR. And it is free, same with the parks. If you stay on site, you get free parking.
The only park I wouldn't drive to is MK. You must park at the TTC, then take a tram from parking lot to get on either monorail or boat to MK. Faster to take the resort bus that drops you off right at MK.
To check out holiday decorations at MK resorts, it would be better to take your resort bus to MK, you can walk over to CR to look around, then hop on monorail to look at Poly & GF (the resort monorail goes from CR, TTC, Poly, GF, MK. From GF, you can take the bus to DHS, then hop on the Friendship boat to BWI, YC & BC. Or walk from DHS.
I forgot to add, from CR there is a resort boat that will take you to WL, which is beautifully decorated too. Just walk to the back of the resort past pool and you'll see the boat dock. This should take up most of the day!
Have fun.