Personally, I don't know why anyone would let others (adults included) handle their iPhones. It's so easy for those unfamiliar to move, mess up, or delete things - not to mention viewing personal things which are none of their business. I always get surprised looks from people when I tell them "no." I'm happy to show them whatever they want to see, but I don't ever hand it over. You wanna take my car for spin? Fine. But not my iPhone.
Maybe the kids would like an iPod touch for Christmas.