The ol' "throw a pebble in the bushes" trick? Seriously? You think that'll empty an entire goblin camp?
I also think any sneaking attempt is doomed to failure. This is an open space, and all of us except Ludo are too tall to dress up as goblins even if we had goblin hoods handy (which we don't). And since these are night goblins, waiting for nightfall would put us (not them) at a disadvantage.
This would put a nail in the coffin of diplomacy before we've even attempted it. I'd rather try diplomacy first, and resort to violence if that fails. We'd lose the advantage of surprise, but given our enemies' sheer numbers, surprise wouldn't make much of a difference anyway.
Plus, sorry to metagame, but the round-by-round combat system makes it impossible to move quickly while fighting. You have to choose one or the other.