How to uninvite someone to a wedding?

Tell those people that there has been a misunderstanding and the wedding isn't going to include extended family and friends but is for immediate family only. then tell the people that instead of the wedding being on say April 19th, we're having a celebration potluck on June 5th whereby everyone brings a dish to celebrate in the festivities of the couple. Then you can invite everyone that was at the wedding along with the 53 people that your mother in law already invited and it wouldn't cost much because its a potluck.