It's a good idea to have children get involved in meal preparation. We're in the beginning stages at home - washing and cutting fruit. I'm definitely not comfortable giving the little one a real knife so we've been using a plastic disposable one that often ends up mashing up the fruit instead of cutting.
Some internet research led us to these plastic cooking knives by Curious Chef. These knives are designed to really cut with the serrated plastic edge but are safe for kids to use. No more smashed fruit! A set of three goes for about $10 here.
Image: Spoon Sisters