Hi Robert, I wonder if you'd be able to post a picture of your raised bed for us?
I'm having trouble picturing a raised bed that big but "raised 3ft. off the ground". i.e. is it a box with air underneath, or is the tallest side of the bed 3ft. tall (which makes sense to me with regard to not having to bend over).
I don't think the cedar mulch will be a problem, as long as it's finely shredded and mixed with other organic material. The only concern I'd have is starting up your bed with so much un-composted material in the bottom of the bed. While organic stuff is breaking down, it uses nitrogen out of the soil so it can 'rob' nitrogen from your plants. It also needs oxygen or it can become stinky and ferment instead of composting. Anaerobic vs. aerobic decomposition.
