This issue is such a difficult one to broach with children.
I was abused as a child and when I had DS, I was paranoid that I may go onto abuse him. That 'myth' has been put to bed now. I was uncomfortable kissing him on the lips, I would never touch his penis unless it was with a wipe and I used to cringe when he was kissed by other people. Counselling helped me get over all this, but I am still a bit paranoid about 'other' people.
We have had lots of conversations about stranger danger, how parts of his body are private and the reasons why I won't allow him to use any websites that have a 'chat or message' facility. He is 9 and all these conversations have been age appropriate. We used to play a game called 'good and bad secrets', which he really liked. You had to guess if something was a bad or good secret. For example 'It is Nanna's birthday next week and Grandad has asked you to keep the present he bought her a secret'. Is this a good or bad secret? 'A friends parent has asked if he can touch your bottom, but you mustn't tell anyone' Is this a good or bad secret?
I am overly cautious about everyone. He only gets to have sleep-overs at his Dads and occasionally at Nanna and Grandads. One of my neighbours, who I am really good friends with, have offered to have him over if I have to go away with work. I have very politely refused their offer. Her husband is a nice bloke, but DS isn't always comfortable with him. He has a habit of tickling DS, but won't stop when asked. I have had to step in and very firmly to tell him to respect DS when he says stop.
I don't make DS kiss or cuddle anyone he doesn't want to - although I do encourage him to shake hands instead. I would not have a partner while DS is still so young - I wouldn't risk it.
Unfortunately, a couple of weeks ago, he over-heard me talking (very generally) about my abuse. I was mortified (didn't realise he could hear us). He got very upset and we have had lots of conversations over the last few weeks. He said that he wasn't upset or scared that it could happen to him - he was upset that it happened to me.
For me, the key is communication. My DS knows that he can tell me anything and I will always listen. I never tell him he is being silly if he is concerned about anything - I listen and acknowledge his thoughts and feelings. You can never completely protect your child, but you just have to hope and pray that you have done enough.