I disagree with Bringhimup. I feel you did a good job with the tattoo scenes. Although I'm not a fan of tattoos it makes sense to use them to hide the runes. Secrets may save their lives afterall.
It was also interesting to get some detail about why Remus never really seemed to be interested enough to connect fully with Harry. In his childhood and later Remus just connected when he absolutely had to connect. Even with the patronus he put it off as long as he could about helping Harry although it was obviously needed. I've always felt there had to be a backstory there to explain it. Good Job! Original, interesting and quirky enough in the detail to freshen up the the old standard plots with a new twist.