I'm going to refuse to help my parents
Why would you refuse to help them?
They can find other people to do stuff for them.
It's wrong not to help your parents when they ask for help. They spent years doing things for you didn't they?
I'm too busy to help them at the moment.
You can spare some time to help them. Even if it is just 5 minutes. If you are truly too busy, tell them you will help after you are done.