I'm going to refuse to work mondays
Why are you going to refuse to work Mondays?
Because I want to be able to spend more time with my family.
It's understandable to want specific days off during the week, but you shouldn't refuse to work a day that you're supposed to. If you want Mondays off, ask in advance that way your employer can accommodate you. If you simply refuse to work one day, you may get fired.
I don't think I will get fired from this.
You would be surprised. You should just work when you are required to.