I'm going to purposely ditch some parents that I was suppose to babysit for.
Why would you break your commitment like that?
I want to spend my time on something else.
You already told them that you would babysit, it's wrong not to do it. Babysit for them like you promised to.
I'm going to make it believable when I tell them that my mom needs me.
It doesn't matter if you have something to do with your mom. You already made that commitment and you should honor that. You're getting paid!