Sailboat Photos Children's Book? I Can't Remember What It Was Called?

Children's Book? I can't remember what it was called? - sailboat photos

We have some short stories, all of whom think the same characters, I, two girls and two boys included (maybe wrong about this). Solving the mysteries of the little things. I remember that probably one of the names of the girl, Abigail, or Abby was short. I vaguely remember the characters in the snow in search of a key to enter a house or something. I also remember one of the secrets of the investment of a photograph or a painting on the wall of a sailboat.
Another story that I think he meant a science fair at school.
Any ideas would help!