I am after book recommendation for kids 8-11.  They aren't super advanced readers, they can read the words, but maybe lack some deeper comprehension as we have kept them fairly sheltered. 

I used to read Nancy Drew, Hardy Boys, but my son found some of those a little scary. Basically I'd like to find some great adventure books for them, some light suspense, mystery, no blood, gore or anything beyond very light violence. I don't want to head too far into weird fantasy right now.

Ideally something I can check out of the Library with Libby.

Thanks for recommendations.