The most enthusiastic Harry Potter age group seems to be the under 12 crowd. From the minute they become familiar with the books (or have older siblings who tell them about the books), kids seem to be attracted to the idea of being a wizard and the magical life that goes with that.
My own kids, at 11 and 14 still love the stories and the movies that were made from them, but they have grown out of their "pretending to be Harry & his friends" playtime games. My niece and nephew, at 6 & 9, are still in their prime imaginary-play years.
But a scarf and hat set based on that bookmark pattern...now there's something any kid could get behind! They could wear this ensemble at recess as they cast spells on their friends! They can publicly proclaim their Hogwarts house affiliation! And having unique winter outerwear can also be a plus when it comes to reclaiming things from the lost & found at school. (Ask me how I know this!)
So last Christmas I found maroon & gold yarn and double-knit a scarf. I used the Gryffindor lion design from the bookmark pattern and monogram letters from this "Harry Potter Font" chart that I also found on Ravelry. I added fringe to the ends of the scarf. The hat was double-knit as well and I added two pompoms to the top just for fun!
If you click into my project page, the second photo shows my niece's adorable reaction of excitement that I caught just as she put on her new winter set.
This year, my nephew has gotten in on the Harry Potter action. My sister told me that there had been some scuffles concerning the Gryffindor set because both kids wanted to wear it while casting spells. So we thought a second set for the nephew was in order. And this dude is not a Gryffindor....he's Hufflepuff to the core.
I wish I had caught a picture of my niece's face when her brother opened his birthday gift. Apparently a new little friend of hers has pledged allegiance to Hufflepuff, which has made my niece feel like she should be Hufflepuff as well. There was a serious sad face going on when she saw her brother's set. If she was a typical first-born, she'd be scheming right now, trying to come up with a plan wherein she convinces her brother to trade sets with her while simultaneously making him feel like it was his idea in the first place. But maybe she's not as cunning a first born as I was...
At any rate, the two sets were a hit and a new Hufflepuff set has been put on the table as a Christmas gift suggestion for my niece. As far as cost goes to make these sets - the gold & maroon yarns were easy to find in a soft acrylic that is sold at Michael's (I believe it was Caron, but I'm not 100% sure that's right.) I think I used 2 skeins of each color and the whole set probably came in under $30. The Hufflepuff set was trickier to find yarn for because the canary yellow wasn't available in the softer acrylic brands at my local craft store. I think I could have gotten it in Red Heart, but I can't imagine wrapping a double-knit Red Heart scarf around my own face, so I didn't want to go that way. Instead, I went with a 60/40 acrylic/wool blend from my LYS - Pacific Chunky. I would have preferred a worsted or aran-weight, but my options for washable yarn in canary yellow at this LYS were pretty limited. And at about $8 per 120 yards, this yarn made the Hufflepuff set more of a $60 project. Still totally worth it for all the use my nephew will get out of the set, and as you can see, it will easily fit him for as long as he is a Hufflepuff!