Unfortunately, the search results do not provide information on creating a specific wallpaper product for a trip to Hokkaido that children will enjoy. However, I can suggest some possible ways to find relevant information:

* You can try searching for "Hokkaido travel wallpaper ideas" or "kids-friendly wallpaper designs" to get inspiration.
* Look for PNG image editing software like GIMP or Adobe Photoshop, which may have tutorials or guides on creating custom wallpapers.
* Check out online marketplaces like Etsy or Redbubble, which offer a wide range of digital products, including wallpapers.

If you're looking for a specific recipe for creating a HD wallpaper product, I couldn't find any relevant information in the search results.