On the top, right click on "Action Target Groups", and create a new group.
I call mine "Ground".
But anything you'll remember will work.

Next, expand "characters" on the top pane.
Then drag from the top pane, to the "Ground" group on the left pane.
Drag every toon, which has a ground target spell.
Rogues if you Distract, Priests if you Mass Dispel, doesn't have to be just DPS.

Next pick a DPS key (FTL DPS), if you want other stuff there too.
Or create a new keymap, if this will be purely AoE and nothing else.

Call it something, or modify an existing keymap.
Set the hotkey to activate.
You'll only need 1 step.
Click on the hotkey name on the left pane.
On the right pane, check the box (2nd from the bottom), "Send Next Click".
In the drop down box, choose "Group (others in): Ground".

If you created a keymap, you'll want to send an output to the toons in Ground.
Most likely, the output will be the same as the hotkey for the keymap.
If you modified an existing FTL DPS key, this is already done.

The Set View step, is a decent idea to include.