I personally would skip the walk the day before the a long run. I find that building up the mileage slowly is much more helpful to me in preventing further injury. But YMMV. I know it's not the same, but you could consider switching the back-to-backs to short run days instead of a short walk-long run combo. I think that would still give you the experience of running on somewhat "tired" legs, and not bump up your overall mileage for the week too quickly.
Thanks, I'll try that. Right now I'm trying to just add a mile or two each weekend to max out at 10 before the race. Fully intend on just walking the 10K and taking it really easy the rest of that day. I tell you what, I am really going to appreciate these medals after the "challenge" training has been.