When terminal gravity is reached, I set the fermenter into the garage, in winter, when the temperatures are anywhere from 20s to 30s. If it gets colder than 20s then I bring into the house at about 55 F. Either way works fine.
I think people are too obsessed with post-fermentation temperatures, cold crashing and all that. The fermentation is done! The beer is merely mellowing at that point, and can do so at any temperature, cold or warm. Sometimes I just do an extended diacetyl rest for a whole week or even two at 68 F. It's fine. You'll still make a delicious lager. No worries.