2 words, City Walk City Walk City Walk
City Walk is right in between both parks, and walking distance or boat ride distance from all hotels. City Walk has Jimmy Buffett's Margaritaville (no explanation needed) a hard core disco, several restaurants, a blues/jazz type club, Latin Quarter, the New Orleans bar (Pat O'Briens or something like that drawing a blank on the name) but its all listed on their website under the City Walk section.
Also, sometimes live bands are playing in front of City Walk, or at the ampitheater there. Or sometimes bands are playing at the Hard Rock. It it is warm you can swim in the pools and order drinks poolside. There is a lot to do on site at night.