If you want the toons to melee...

Ensure you have Click to Move (CTM) enabled in Interface Options > Mouse Options.
Then set an Interact With Target (IWT) keybind in Keybinds > Targeting Functions.

Target the bad guy.
Assist so they all have the target of the active toon.
And then press your IWT key, which will have them all run into melee and start auto attacks.

If your team is ranged, and you just want IWT for facing..
You could have another key, such as S or Down Arrow to broadcast a stop movement.