The problem is not you...you can do all the right things to avoid this kind of thing...but all it takes is even ONE FALSE allegation for you to end up in deep water.
That what scares me about this kind of thing. I also was in a job right out of high school that caused me to have to work with teenagers. I was a social worker that would often have to transport kids from foster home to foster home or police station to foster home. There were several times I had to transport a teen girl alone...I tried to do everything I could to protect myself like record milage, and even bring a tape recorder with me and tape the whole trip.
Finally I just got too stressed out about it and decided the job was not for me. And you know what, later, after I left the agency, I heard there were some false allegations made against a foster parent.
Not to scare you, sorry if I did that. What you are doing to great, just protect yourself.