Cousins

Originally we wanted to invite children, but it would've taken us over budget so we made the decision to cut children from the guest list. The problem is he has first cousins ranging from 8-35 years old. My fiancé is closer to the older cousins and hasn't even seen the younger cousins since they were infants so we didn't plan on inviting those under 18. This is now an issue with his former aunt because she is the mother of two of the cousins that are under 18. She has been very mean and accused us of being racist because she is African American and his cousins are half. They aren't the only first cousins not invited. He has two other first cousins that aren't invited because they are also under 18. We also didn't invite her as she is his uncle's ex-wife and we didn't think it was appropriate for her to be there when his uncle and his wife would be there. As a result, his mom has also been giving us a difficult time because she doesn't think it is right at we are inviting some of his cousins, but not others. Any advice?