I haven't stayed there, but your upgrade sounds like a pretty big deal to me. The link below is from a post by PlatinumPrincess about her "Unbelievable" stay at Wardman Park Marriott.
Post back after your stay to let us all know how much you enjoyed it.
I was upgraded to the Presidential Suite at the nearby Bethesda Marriott a few years back--if it is as nice, you are in for a treat. I had a dining room table that seated twelve, two wet bars, 2 half baths and two adjoining rooms, each with their own baths. Let us know the outcomes and youyr secret for this upgrade!
Regarding the questions of "being upgraded in advance" I have also gotten the impresssion that I have be pre-assigned to an upgraded room/suite. The reason is that when checking in, without comment from me or the front desk clerk about my accomodations, I am given the key in the paper jacket with the room number on it, and when I get to the room, it's a suite or a larger room than normal. This has happened to me several times and several locations. I have been told by the WDM Marriott staff that I am upgraded in advance on the day of arrival if an upgrade is available at that time. Other times, I have asked and sometimes get an upgrade and sometimes not. One thing I have noticed is that when I make my reservation by phone using the platinum reservations number, the agent always tells me they are adding a note requesting an upgrade. Many times it works. There used to be a place for special requests/comments when making an on-line reservation, but I think it disappeared along with some of the features on insiders.