There is an easier way to clear the courtyard if you do so before they are automatically hostile. Somewhat spoilerish, so:
Get all but one character up high, per the previous advice, then...
Send the main character down with a bottle of poison or acid. Use invisibility to poison the vat the goblins are drinking out of (acts as a crafting station). You get a toast scene, about 1/4 die outright and about 1/2 the rest get injured. I said to send the main character because there is a dialog bug that might happen if you use another character.
