Looking for an illustrated children’s book (perhaps 12″x”12 and ~48 pages) about a group of kids who discover and clean out an old abandoned cabin in the woods and fix it up, paint it in vibrant colors and decorate it. I read it at my public library in Vancouver, Canada in c1974 and remember it being full color on all pages so am guessing it was published in the early ’70s. I can’t recall the title or the author. That book was so magical because the kids had a secret playhouse in the woods that no one knew about. There was no adversity/bad in the book that I recall (other than overcoming the shed’s dilapidated condition) and I believe it ended with the kids hosting a party there?????

Thank you in advance for your efforts to figure out what the book was.