If that real world is critical to the story, it can be explained in advance so they are not shocked, and discussed afterwards when they have questions. I feel quite comfortable having frank and truthful discussions about drugs, sex, and rock and roll. It is communication that will help them survive, not full fledged sheltering. The Internet has not evolved to the point where one can depend on a cyber sitter to do our work. That's just fine with them.
Children are so smart today.
A little communication can to a long way. Parenting can be one of the biggest challenges one will ever embark on. Some things you just have to screw down tight and explain the locks. Open the doors for the things that are age appropriate and support their efforts. Finding that balance is impossible.