I have various heucheras in morning, midday and afternoon sun. One or the other -- not all at the same time. I think most do well with a few hours -- just not all day.
I would go ahead and plant. If it burns, just move to a shadier location.
Also, I've started growing many of mine in pots and sinking the pot in the ground. It seems, so far, I'm having better results. If you did that it would be easier to move if the sun is too much for it.