Balancing gamer and parent

When I was a kid I used to bitch about game censorship, but to be fair I think I was about 13 by the time a game dropped an f bomb on consoles, flash forward a bit, and now I have a 6 year old son, who is ravenous about games, and robots, and zombies, and explosions. It makes for a difficult situation, one that I think each parent has to really weigh themselves. I still bitch about censorship, but am thankful for things like ratings, and wish they were a little more thorough... I'm in the UK, and the bbfc do an ok job, but  terms like 'moderate violence' covers a lot of ground. Being a fan of games as well, it's easy for me to pick up a controller and use my own good judgement to decide, or in best case, sit and actually play with him, ( even if that means I may have to see the ending to Lego Star Wars a few too many times...).  
One thing I have noticed is my son is really taking a liking to open world games, which is sadly a genre that tends to skew more towards the adult end of the spectrum, Just Cause 1 and 2 weren't too bad (under supervision, and avoiding certain areas) and Burnout paradise was perfect. I just wish there were more games that allowed him to explore an environment, without all the 'grit'. As I side note does anyone else have any other suggestions?