Kids are real impressionable, at any age.
Just be choosy about what they play... ie: age appropriate.
My daughter, plays computer games too, watches tv., and we have a Wii fitness thingy. It's good, in that my daughter and us, choose the 'educational' things for her. And we play it together as a family and choose games that are fun, but not violent or 'sexualized.'
BUT... we limit her usage... and she can do it only as a 'treat' or if she has done her other chores or homework. So it's fine. And it's certainly not something she does everyday. Only about once a week.
Now, my daughter's friends have older siblings... and so THEY watch and play games that are "teen" oriented already... and it seems these kids are way too 'sassy' and their behavior is different, than say kids who DO watch games/shows that are age appropriate. EVEN MY DAUGHTER will tell me this... that her classmates that watch TEEN shows are 'sassy.' My daughter is 6 years old... and her classmates watches "Hannah Montana" & "Cheetah Girls" and "High School Musical" already, and the more teen oriented or adult oriented cartoons. My daughter's Teachers have also said that yes, these kids should not be watching it... but it's hard to control, but they see it in their behavior and clothing choices and attitude. One of my daughter's classmates made a comment once saying "I don't watch PBS, it's only for babies... I only watch Disney channel and Hannah Montana and Cody." When I heard that and my daughter pointed it out (I over heard this girl saying this), I just thought - EGAD! How sad...
For our girl, we really watch what she views, and often talk with her about what is appropriate or not... and why. We DISCUSS it. Not just talking 'at' her about it. THUS, my daughter has for her age, an ability to 'discern'. AND, in terms of my 2 year old son... my daughter is not allowed to watch anything besides PBS or certain Noggin shows, in front of her little brother. She COMPLETELY understands. Completely. WE choose what she watches and we explain why.
But in school... they do learn about computers and use it. So you can't keep them in the dark about it... and in school they learn all about these shows anyway. My girl, she learned all about these "teen" shows from her friends at school even though she does not watch it herself. And yes, it is enticing to them. So...
Anyways, sorry for rambling.. but yah, just do what you think is best for your kids and your comfort level.
Just to clarify, I know each child and parent is different.... and if they do watch 'teen' games/shows at 5 or 6 years old it does not mean their kids are 'sassy' or worse off. I know it varies.
All the best,
Susan