2 inches is pretty thin if there is no mulch in the bed now. If your just topdressing whats there now, that's ok. Normally if there isn't anything in the bed, you should go 3-4 inches. It will settle some. Assuming your measuring and calculations are right, and you came up with 6 yards, and the terrain is flat, I would charge 470 which includes labor for 2 guys and delivery. If the terrain is hilly and the beds are hard to get to, I would charge $75 per yard. Edging would an extra 0.75cents per foot. 200 feet, is $150.
With that said, I moved 4 yards of mulch by myself, at $70 a yard, in 2.5 hrs. About 1 yard of that went to the back yard, down a hill. That was 2.5 hrs by myself. We get mulch for $25 per yard, you do the math. Im not sure how you came up with 5-7hours for 2 people, especially with 2 barrells..
I would go out of business if it took us that long.