CloudKit share private Container between users

I'm planning to develop an App used to share infos about geographic locations (coordinates, notes, pics), a kind of Treasure Hunt and I did not understand if it is possible, using CloudKit, to share part of a private container between users. If it is, how can I do that? I'd need to create something like Apple does in the Reminders App, where a user can "invite" other users and have a common list to share between them all where everybody can insert or edit stuff.

Eventually if it's not possible to do it using CloudKit, can I do that with Parse?

Thank you!