If I can learn how to use all the controls of Black Ops, anyone can. It's the twostick system to move around. The booklet they put inside the game should provide the control set for you to familliarize yourself with. I rented it, and someone stole the booklet, so I had to go from scratch. I still am getting kills in live, online play (which you would have to go to "Multiplayer" to access. Campaign is just on your own) but my kill to death ratio is raunchy.
And with a lack of vision, COD has most certainly made me curse it. And the people that literally spend hours a day playing it...hence, they are very, very skilled. So starting out, you may want to cover your little one's ears.
And yes, if you do "Campaign," you're killing computer simulated enemies with a storyline added to it, but if you go online, you're eliminating human enemies logged on with you.
Hope that answers everything.