You can do this in Keyclone, but it doesn't work very well.

Click Set Up.
Go to General.
Halfway down, there is an option "pass mouse click hotkey".
Choose a hotkey and then put a check mark into one-click then off.

If your group only has a single AoE type, you could make the hotkey the same for both the Keyclone mouse click and your DnD macro.

I'd suggest a hotkey to turn the broadcast on, and then a different key for the spell.
That way, it will work for any combination, with ground target spells on any key.
Or for say Balance druids who have Hurricane and Force of Nature.

With Keyclone, it will physically PiP swap, which is not the fastest.
With this feature, you're basically losing control of the interface for a few seconds as it PiP swaps and then clicks in each window in sequence.
Which could royally suck in some situations.