First of all, what is the FULL name of the Laptop? For example:
ADVENT Roma 1001
or
ADVENT Verona P
etc etc
Do you have a 'User Manual'?
I suspect you HAVE actually lost connection to the internet. I note you say 'if he types in a web address the internet works fine', but can you actually 'surf away' from that page? I'd be surprised if you can. I suspect the reason that you are seeing web pages that he types in is because they are held in the 'cache' of the computer. That basically means the web page is stored on your computer but if he tries to type in the web page then click on refresh does the page actually refresh or does it show 'this web page cannot be displayed'. If you're not sure about any of that, try typing in the name of a page you have never visited before, anything will do....
Here's some examples:
http://www.number10.gov.uk/ I doubt you've been to this one unless you're VERY interested in politics.
http://www.clockswatches.com/ Again, unless you're interested in clock/watch repair you've probably never visited that site.
Try one of them or one of your own as long as you've NEVER visited it before on that laptop. Can you see the web page or are you getting the 'this web page cannot be displayed' message again?
If you cannot see the web page (and I suspect you won't), then the laptop may have lost contact with the router.
If you look at the bottom right hand corner of the screen (near the clock), you should see a little icon that looks like two computer monitors. Does it have a RED CROSS on it? If so then you've definitely lost connection. Float your mouse cursor over the icon. What does the message say when you float over it?
When connecting a laptop to a router wirelessly the laptop connects to the router with something called 'wifi' (you may have heard of that before). Some laptops have a button for turning wifi on and off. Your son may have knocked off wifi. Check that first. If you have a User Manual it will tell you which button controls the wifi. When you float the mouse cursor over the little icon mentioned earlier (bottom right hand corner of the screen near the clock), it may say wifi is off/on. If it says 'OFF' then he's probably knocked the wifi button. It just needs turning back on.
Failing that, are there any other computers connected to the same router? For example are you using a Home PC to connect to this forum? Can you test for an internet connection with that computer using the same router?
If not then we need to find out if the router is indeed connected to the net. Has the router got any red or orange lights on or any green lights off? If so then the router has probably lost connection with the net. Try resetting your router. Some have a small 'hole' at the back (where the wires go in/out). Push a pen into the reset hole. If you can't find a reset hole just unplug the router from the mains for a minute or two then plug it back in. When you plug it back in look to see if all lights come on and are green (or that the normal sequence of lights is on). If you still have a red light or unusual sequence of lights after resetting the router then there is a possibility that your internet is down. You'd need to contact your internet service provider if that is the case but saying as you are connecting to this forum I'm assuming you still have internet at the house?
Once the router has been reset it might be worth restarting the laptop as well and seeing if it connects to the router.
Report back and I'll see if I can be of any further help or one of the other guys will pick it up from here.
Glad you got sorted. Don't be too hard on him, us boys will be boys you know?! 
