Sherlock Holmes is selfish, arrogant and condescending. The Hardy Boys (despite their girlfriends) are probably a better influence.
Personally, I don’t feel that there is any problem with 99% of juvenile books written before 1980 or any book written before 1930. But if you really want your kids to read stuff that you are certain won’t have a bad influence on them, then they should only read books by Marcus Lehmann.