So many ways to approach it.

Like go in friendly and then casually spread out smokepowder and wine barrels all over the yard. Get up to the drunk hobgoblins and toss fire. Boom!
Then there is the poison option which i believe requires invisibility, dexterity and thieving skills. Mix??

or agree to the raid, backstab both sides. But not before having druids and tieflings murder eachother. Watch from afar as tieflings and spiders kill eachother. Kill any survivors.
Before that kill any remaining goblins with bombs.

Guess the path forward will have to rely on Volos advice? wink
Just gotta make him caged before blowing up the yard.