we used to stay at fw all the time...
any monorail resorts like at the Grand Fl. contem or poly take the contem boat from the fw dock and get on the mono (thinking it runs till at least 10, same with the boat but not sure how the party would change that, at least an hr after park closing) would also work for any epcot rest.
if there is a party going on that night at mk i would guess you should have normal bus transportation from there to any resort. during the party....again take boat to mk from fw dock and go from there or if it's not a party night or from
any place else take the buses. if epcot is closed ( or it's close to it closing when you might wait along time there) you'll have to go to dtd but actually the party probably works in you favor here...i'll have to think of that when we go in dec with the xmas party and buses!
we've been to wdw a number of times but the driving is confusing and there is always a lot of traffic so it's not like you can drive like a granny and read the signs, esp. at night...we drove once on one of the first nights last trip and husband( who drives in city traffic all the time) said never again! it's nice, but longer, to take the bus usually ( had a couple horror stories last time but oh well take the good with the bad)