If you ferment at ale temperatures you won't get a true lager character with most lager yeasts. Your second idea will work but will indeed take a long time. A third option is to try one of the specialty lager yeasts that ferment cleanly at ale temperatures, that is, the "California lager" (steam beer) strains. Your situation sounds like exactly what they're meant for.
(EDIT remember, it's in the fermentation, particularly the very early stages, lag period and logarithmic growth, that the temperature-specific flavors of fermentation are produced. Lagering just helps to physically clarify and stabilize the beer. You don't actually have to "lager" a lager at all if you fine and/or filter it.)