It is good advice to talk to them about it...keep it in line with their age. And you should try NOT to scare them. Unfortunately, statistics show that talking to them will not really change anything should an abuser approach them. There is simply NO way to warn a childs mind against the machinations of an adult mind. The best you can hope to accomplish is to have paved the way to discussing difficult things with your child, so that they may feel more comfortable opening up to you.
Now, that's not to say there's nothing you can do. There is simply NO SUBSTITUTE for keeping an eye on your child pretty much at all times. Be on guard WHEREVER you go! If you're visiting relatives, and all the adults are in the kitchen and your kids are off somewhere playing with all the other kids...GO LOOK IN ON THEM. Make sure they're not off in a locked bedroom or out behind the barn or whatever.
If you have a relative or friend who seems especially close to your child (no I'm not encouraging paranoia here) keep an eye on them. If an adult EVER seems to show undue interest in a child, especially wanting them to spend the night...ask yourself why?
When your children get older and want to spend the night at a friends house...be VERY careful. Remember, the younger your child is, the easier a target they are. I wouldn't let my kids spend the night with anyone until they were 10 or older. I WOULD let them invite friends over to our house instead. Trust me, the other parents don't mind if you're the one doing all the work! But don't forget...you have to be on guard against other children who may have been molested practicing whay they've learned on your child. So again...have them sleep out in the family room...and then GET UP in the night and check on them! There is just no sustitute for a diligent, caring parent.
To my knowledge, I managed to get both of my boys past their childhood without being molested, which in my family is practically a miracle! But the cycle is broken.
Take care of those precious babies, and don't ever let your guard down until they're older.
Tracy