As an avid mystery reader, I'm a big fan of the Stop You're Killing Me (SYKM) website (http://www.stopyourekillingme.com/). The site is wonderful in that it offers you easy access to mystery books, allowing you to search outright, or if you remember the main character name, by character, or by author. This alone makes the site noteworthy, but it also includes some other handy features including a "read-alike" section, a genre index and and location index. While the site does include some mysteries written for the young adult, it does not list mysteries geared specifically toward children. However, Lucinda Surber, SYKM Webmaster, has another wonderful site called Bookworm for Kids (http://www.bookworm4kids.com/). The site is geared toward parents, grandparents and teachers interested in encouraging kids to love reading. There are links to Caldecott and Newbery Award winners, links to books by theme (such as divorce, sibling rivalry), books by genre and by subject, and more. If you want to find some great recommendations for mysteries for children, just visit the site's genre link and select "mysteries".
Enjoy exploring these wonderful sites and happy reading!