Welcome to the forum.
You probably know that Tuck will be more your pet than Charly's since a turtle is a see and not touch pet for children. And all the care and maintenance that is required to keep these wonderful creatures healthy and happy is definitely not child's work.

But if simple hygiene rules are followed there's no reason why occasionally Charly can not touch (pet) her turtle (but always supervised of course). And if taken care of properly with the correct habitat and care, Tuck should be with Charly well into her adult years.
If you have any pics we'd love to see them.

If you have any questions after searching/reading the main site and the forum, don't hesitate to ask.