MP's are in charge of procurement. Take defense. If you have no experience procuring weapons / aircraft / whatever how do you know you are getting a good deal? Sure there are advisers and whatever but surely before you approve say a £10B pound submarine project you should know something about submarines, who builds them and what is a reasonable figure to pay?
I feel as well that one person cannot be responsible for such a broad range of topics like "Culture, Media, and Sport" which the Internet inevitably falls in to.
Regarding the point about "children are more technically aware than their parents" I think it is invalid. I think as a parent you need to involve yourself in your children's lives. You need to get up to speed with what is current. The excuse of "I'm old" or "I'm not hip / tech savvy / whatever" doesn't fly. It really isn't difficult to ask Google how to filter web content. Just as it wasn't difficult for me to phone up my TV provider and ask how I hide the adult channels on my TV.
You don't need to be a genius to work a computer. You just need to apply yourself a tiny little bit to do whatever it is you are trying to do.