To Give a Plus One or Not?

My fiancé and I are having an intimate wedding with approximately 30 guests in April 2021 and will be sending out invitations soon. We are paying for the wedding ourselves and want to celebrate with close family and friends. Essentially, none of our guests are getting a “plus one”.


Here is the dilemma: my Uncle and his two sons from a previous marriage mean everything to me and I would love for them to celebrate with us. They have received our “Save the Date” without a “plus one”. However, my Uncle’s girlfriend of about one year recently expressed her excitement in coming to the wedding to my Mom although we did not intend on inviting her. She also stated that her daughter would be coming. I’ve met his girlfriend one time, but have never met her daughter.
My fiancé and I want our wedding to be intimate and I am conflicted on how to handle the situation. On one side: I’m paying for my wedding, thus I designate who attends. On the other: I don’t want to be rude to my Uncle.
I really don’t want my Uncle’s girlfriend and daughter to attend. What are your suggestions? Invite the guests out of courtesy or invite who we want to attend?