First grow cabinet to outside questions.

I germinated 16 kush seeds and 6 feminized buddha seeds. About 14 total have sprouted 5 fem buddha and the rest kush. I plan to keep about 6 plants for the box and transferring whatever else makes it outside. My questions are how long should i leave them in the small styrofoam cups? Also is it a good idea since some of these are going outside to let them sit outside for about an hour a day to get used to sunlight and outside conditions?