put them outdoors in a sheltered spot for about a week. Out of wind and out of sun, like inside a fenced enclosure, etc. to get those leaves toughened up. then out into more sun. Of course your watering schedule is going to change depending on the sun/wind exposure. More sun/more wind outdoors will usually end up needing more water. But since they've been inside and it's cool inside, it could be just the opposite at the first when you put them out.
Night temps of 60 are plenty warm enough for a banana. After they've been acclimated to outdoors, most can handle 45 with no damage.