I'm currently transitioning one of mine to go outside. I would suggest a transition for yours too, because the big, wide world otuside can be scary with very, many new noises.
I'd start with a short amount of time (maybe half an hour) and gradually increase it up until they are clearly comfortable being out there from early in the morning until late at night, and then keep them stable like that forr a few days (bringing them in overnight), and then just go for it.
Wherever they live inside, have they been used to fresh, outside air? What are the temperatures they have been used to?
If they have only been used to house temperature (roughly around 18 degrees), then its still too cool overnight (some nights) to put them out unless they are used to colder temps in the house. They will need a longer transition if this is the case.