Do you think I should cut my child-free kids out of my will
That's up to you my friend. Why do you want to cut them out of your will though?
I don't like them because they never visit me and I'm old now
It is your decision to do what you want with your will but it shouldn't be done just because they are child-free. If there are other reasons it is okay but not just because they don't want to have children. It will hurt them and will cause them to hate you.
I don't care and it's none of their business, they are not really my kids anyway.
I guess you know what you need to do then. Whom would you give your assets to if not your kids? At the end of the day, you worked hard for your money, so you make whatever decisions you deem right and it's normal not to pass things down.