The consensus response to the OP is to realize that the area is too difficult for your present level and to come back later. Although I agree that this is the sane approach, I've never claimed to be sane.
First, it is possible to detect the traps at level 3 as long as one member has the Light Stepper trait. Second, as long as you accept that it's not going to be easy, it is possible by dint of wit and speed for your level 3 characters (at normal difficulty) to defeat the level 6 orcs.
The general approach is to create a barrier from crates and barrels, lure one orc close enough to use teleport, and teleport the orc to a bad place to kill him, run away to end the fight and repeat. Since the shaman is the most dangerous, I killed him first. With the barrier in place and a poison barrel next to a mine, I summoned a spider on the orc side of the barrier. As the orcs approached the spider, I teleported the shaman onto the mine next to the poison barrel. The exploding mine did most of the damage, with the poison from the blown up barrel doing the rest. For another, I did the same, teleporting the orc onto a mine in a pool of water. The exploding mine did a good bit of damage to the orc and caused the water to become electrified, stunning the wounded orc. My troop shot him with arrows while he was stunned until he was dead.
I agree this isn't the most efficient approach, but sometimes it's fun to see if I can win against "impossible" odds (I think I can see a windmill in the distance).