I'm not authority in the subject, but here's some of my thoughts:
Challenges are made to be followed directly as written. So you will probably be advised to do just some 2-day template.
I'm however in the same situation with you. I'm planning to do the challenge with 3d/week (5 week cycles).People usually try to add things to challenges and then exhaust themselves while doing the program. In our situation we're going to make it little easier, and I personally don't think that as a problem with progress. We'll see if this does work or not.
I really can't say anything significant about your main question. I think you'll be okay when doing just one week (2 days) deload. The full-body deload would work here perfectly (3x5 each movement - really light).