A couple of my favorites are listed here, which I definitely would agree are great adult places: Vinyard Room and Yukibumi (spelling may be off there). i'm not necessarily a big fan of the long walk to PPH, but as it's the only Japanese place on property, I suck it up.
Blue Bayou may be an idea too, depending on your idea of "adult." I took a friend there Sunday (it was her first time at DL. On the adult side, it's meant to be a quiet place. The riders may sometimes get boisterous (and maybe some of the people eating too), but it's definitely upscale. No alcohol though, if that matters.