WHAT? A window? No, no, no.
Tinkerbell does NOT need to "come out a window".
She simply flies up to near the top of the castle and hovers there until her CUE.
She then "blinks on" her "fairy-lights" and flies very near a small wire that's strung up between the castle to just above the Noodle Station Restaurant.
She used to get so excited that she would just "fly all over the place" and could get lost and might get in the way of some of the fireworks, so...
Peter Pan asked the CMs put up the small wire for her to follow along so she won't get into any more trouble.
If you look in the daytime, you can see this guide-wire running from the castle.
If you relate this info to the kids before the show they'll know where to look for Tink.
(I hope she remembers to "follow the wire" and not get lost.)