I'm 13 and have and Original iPhone 8GB and an iPod touch 2G 8GB. I got the touch 1G on my 12th birthday and then sold it a year later to get the new touch. I only had to pay $46.00 more to upgrade. As for my iphone, I used my paper route money and Christmas tips to but a used Original iPhone from my neighbor. it was $250.00 I had to use my cash and work to get them, but I really take good care of them. I don't use my iPhone much. It spends its time sitting in it's box, but I use my touch everyday. I have a hard case and silicone case for both of them. I don't use the iPhone as a phone, go figure. I just use it as an iPod touch with a camera. I would say, If one of your sons want it, have them pay $199 for something. When they earn it, they will most likely take good care of it. My iDevices have no scratches on them and have never been dropped.
When I was younger, I had a 1st gen shuffle that was given to me for Christmas, and it lasted me two years, before I dropped it on concrete and it got stepped on. The headphone plug was broken inside the jack.
But I think If someone earns something, they will take care of it better.
Typed on my iPod touch 2G