We walked this last year. We were there 4 days, 5 year old, 66 year old mom (not in great shape), and me. We took ART twice and walked the back way the rest of the time. It's way easier to walk back from the parks because you can cut off significant time by going through Grand Californian instead of around the DL hotel. We would walk to the crosswalk, go down Disney drive and then around the Disneyland hotel into Downtown Disney. We like staying on the backside personally. We took ART to the parks twice, and back to the hotel twice, we go back to the hotel every afternoon so we walked way more times than ART. For us the bag check line on Harbor made walking the back way worth it. I think they may have addressed that issue but last October while we were there the lines were horrible. Dtd side we never waited longer than 5 minutes.
I can't figure out how to put a picture of our route in here while on my phone. I'll do it from a computer in a bit.