Our 10-year-old's total ??? Fan, so I decided this year for this Advent. Since each is solved tomorrow before school a mystery. It makes it a lot of fun and the rewards are far too well received, even if they are qualitatively evaluate rather low. This aspect does not hurt in my eyes but the overall judgment.
Attention: clever (? Lazy) Detectives is a great temptation to erspickeln the puzzle solution on the back of each puzzle sheet, so parental supervision is mandatory in such a case :-)