Ok, I have the spells and will post Saturday morning.
One last delay for any last posts because I am tired anyway. A quick note about the spells:
Stinking cloud and sleep - both could be cast if you move up 30' (Normal movement - not super stealthy beyond the spells big bonus, but it seems like you would get first action if you did.) This would put either spell centered on the guy 20' in front of you in the middle of the road. Either spell would include the two front archers, the guy in the road and the guy on the rock. You could potentially get the woman holding the horses head as well but that would also include D'Harum and the horse and so according to your description is not what you want to do. With the way you have it listed right now I am assuming stinking cloud is the spell of first choice. Also, if you cast sleep remember that you can cast it at higher levels to potentially put more HP of opponents to sleep. But if you wish to do so you need to make that clear.
Web - Only has a range of 60' and would thus need two turns of movement before you could cast it. In fact, you would need to be in front of the two back archers current position to be able to target a spot in front of the horse and cart.
Everybody else - this is your last chance to add a reaction to when the spell goes off. IF, and it is an if at this point, you get the drop on them with the spell it is possible that all of you could act before they get a chance to do so. (In other words, you all take an action, then I roll initiative to determine order of actions on the next round. But they don't go before then so you essentially get a free round.) That assumes they don't also intend a sudden attack, of course, but you wouldn't know that. Right now all you know is who stepped out of the woods and what they said. Anyway, the point of this paragraph is to say - if you want to do more than just move up when the spell goes off (arrows, axe swings, staff smacks, or whatever) now is the time to be clear.