Halo 5 local multiplayer with non-Gold accounts

I've added my kids' xbox accounts to my Family setup on Xbox.com,
but can't add them to my Halo 5 fireteam.
They have Xbox Live accounts, but only I
have a Gold account, and my Xbox One is set as my home system. What
do I need to do in order to play multiplayer with them
locally?

Here are the symptoms:

-- They show as "Not Joinable/Not Spectatable" in the "Friends"
view
-- If I log in as one of them and start Halo, a screen comes up
that says "ATTENTION | A fireteam member's online safety settings
do not allow them to view this content"
-- If I invite them to join my game, party, or fireteam, then use
the controller they're logged in with to accept, it returns to the
"Friends" screen with no addition to the fireteam

Here's what I've tried:

-- Setting the Xbox One as the Home System for my Gold Account

-- Adding them to the "Family" group in my Microsoft Account (and
confirmed when logged in as them)
-- Added them as my friends
-- Removing their accounts, restarting the system, and re-adding
their accounts
-- Setting their controls to allow everything for Friends

Any suggestions or settings I should look at? Or do I really have to upgrade all my kids to Gold accounts just to play together on our local Xbox One?

Thanks!

:)