Follow breaks once melee starts.
With bears there are a few solutions.

You can talent so you always get 10 rage when you shift into bear form.
And then Feral Charge (also a talent) your opponent.
Probably won't have these yet...

You can keybind (Escape - Keybinds) a hotkey for "Interact with Target".
Enable (in Interface - Mouse Options) "Click to Move".
Target the mob, have your slave assist, then click your Interact With Target hotkey.
This will have your toon run to where the mob was, when you clicked.
And then melee is auto engaged.
If the mob moves, click the interact again.
This is the preferred method for melee toons.

Alternatively, run your main through the mob, with your slave on follow.
Turn the main around, and the slave(s) will also be facing the mob.
And the mob will be between your two toons.
Eventually, you'll probably spec them both as cats if going Feral.

With two druids, you could also leave one in caster form.
Break follow and nuke away.
And maybe toss a heal or two to reduce downtime.