How do you let you mum-in-law know that you will be calling the shots on the upbringing of your child (without sounding rude)?

I've seen firsthand that it takes a village to raise a child. A MIL's insight might deem helpful in some form so listening can't hurt. When it comes down to it though, being definitive, purposeful and firm with decisions sends a message to the MIL that you put careful thought into raising your child and will take full responsibility for the outcome.