Wanting to burn a Cat 1-4 certificate this week for a Thursday night stay near ATL. I'm looking at either the Airport FS Marriott or the Airport Marriott Gateway as those two look to be the best value. 1st question: Each property has a park and fly package for $10-$15 more than the normal rate. Is there anyway to use a Cat 1-4 cert and pay the incremental charge for the Park and Fly rate, or would I just have to pay the normal parking fee to leave my vehicle for my trip? 2nd: Any recommendations between the two? I've stayed at the older property before and it was nice. I'm gold if it matters. 3rd: How do I actually use the certificates to book the room (sorry if that's a newb question.)

Thanks in advance.