I used to following workaround, since Microsoft is "ignoring" us and making us go back and forth between different services...
I used the Outlook client (but this can be done throught the webmail too) and made a new calendar, right-click on it and shared it with my family. They all received an email to accept the calendar sharing and everyone is now happy.
Kids are having the calendar in read-only mode (which I chose) and my wife and I are having full access to this specific calendar.
I did have to make a lot of copy / paste between the "old" calendar (that was still available online) and the new shared calendar that I created on the Outlook application (in my Hotmail's account).
Not elegant, but working...