Q: Family Sharing options?

Which purchased content can I share using Family Sharing - Apple Support - http://support.apple.com/HT203046

"The family organizer can turn on Ask to Buy for any family member who isn't an adult."

Request and make purchases with Ask to Buy - Apple Support

If they are defined as being adults, I think the iTunes Store uses their Apple ID to make purchases, not your Apple ID (whether they are in Family Sharing or not).  You should have them sign in (enter their Apple ID and password) here

https://appleid.apple.com/

Have them show you the screen showing their Payment Method.  Maybe your credit card is entered as their payment method.  If that's the case, have them remove it and buy an iTunes Gift Card (for themselves), which they can redeem as iTunes Store credit.

The Organizer has to provide a credit card or debit card (Credit if you have non-adult family members).  The purpose of that card is to cover purchases of the family members.  That is clearly explained in the documentation for family sharing, and is also presented during the Family sharing set up.

Sorry.

None of the replies answer the question you posed:  How does one share ONLY a calendar with a family member (whether in Family Sharing or otherwise on iCloud)?  Don't want to share ll the other purchases and item etc.