I'm not against splitting up in all circumstances, I just think it's a bad idea in this case because either there really is no further danger in the forest, in which case we can just disguise the wagon and have the advantage of greater numbers storming the goblins, or there are further dangers and so we ought to stick together for safety anyway.

OOC, I also think that we can't necessarily count on encounters being easier just because we have more people, and also that it's not good to split up at the very beginning of the adventure. Also, if the first group really is gone a long time, that's essentially just cutting half the characters off from being in the adventure, so...