When the children are not around go on the websites and view them yourself. This will give you an idea what its all about and what would be appropriate. If something is inappropriate make sure you don't let them have access to that site. You can deny access on your computer.
It's not a bad idea to stick with the websites that you are familiar with unless you are near your child when they are online. Otherwise you can install parental control software to filter out unwanted content.
Most gaming website will tell you what the target audience is for their game(s). Try and look for a ÈFrequently Asked QuestionsÈ page, or an ÈAboutÈ page, which should tell you more details about the content of the game.