Yuna will definitely be a kid during the event. As a young girl we was adorable but she lost her parts pretty early so she will probably wonder around and potentially get in trouble. She was overly curious and used to being able to do whatever she wanted because he father was important before he died. Over all she will just make anyone who encounters her worry by jumping off of things, climbing on things, crawling through small spaces, maybe even getting stuck and then doing all that again just for fun. 12 around the age that Yuna started showing her rawr magical talent so that might come up as well.

Ellie will not be in this plot because once she hears virus she will be locking herself in her room and not touching anyone. Some habits die hard.

Kitty is new to the game so I don't know what I'm doing for her just yet. She is a young werewolf so if she turned into a kid she'd just be a regular snarky kid who's into being a DJ. I imagine as a child she liked breaking rules but suddenly not being a werewolf again will throw Kitty for a loop.