This morning I took a look at my twelve-year-old and told him I thought it was time for a hair cut. He turned to me and said, "A really good hair cut can change your DNA and make you truly sexy fine."
How do you respond to that. The kid is twelve. And where did he come up with that line.
As to what to do with it, I say, write it down. Save it for a writing reference. Use it as an idea to start a story or build a character. It's too precious to let fizzle.
Kids say stuff all the time that you can work with. When one of my kids was about three he was eating his breakfast and he looked up and said, "Mom, who invented fried eggs." I made up a story about a caveman accidentally dropping a pterodactyl egg on a hot rock and he was happy.
Are you taking advantage of your kids when you take their lines or questions and use them to further your writing? According to my husband, it doesn't matter. We only had them so we would have some one else around to do the dishes.