Danielle-p I think a mutual keyholding arrangement is best done with a romantic/sexual partner, where unlocking for shared relief is an intentional part of the arrangement and not a loophole. Not for a family relationship where a sexual dynamic between you would be grossly inappropriate.
That said, if your relationship is more a matter of being accountability partners, rather than a classic keyholding dynamic, such an arrangement might work. Basically, when there is a reason to unlock, you get together and agree that it is the proper step. The keys being stored in a way that they cannot be used without everyone's knowledge (e.g. single-use seals for emergency keys and a multiple custody lock box for the main keys).
But one more question: what is your existing chastity arrangement like? Were the girls happy to wear their belts or did they need encouragement, and what form of incentive did you provide if the latter? What are your objections to masturbation, and do your daughters agree with them? How do you handle hygiene needs?
