Engagement Party - how to handle upset family

My mom is throwing our engagement party. We wanted to keep things small so we only invited our immediately family, bridal party and a couple cousins we hang out with regularly. Now, my fiancé has 80 cousins and he only invited 2 to the engagement party because they are the only ones he regularly hangs out with. It turns out some of his other cousins are mad that they were not invited. All of his cousins will be invited to the wedding. We’re seeing his family this weekend, do we address this issue with his cousins? We don’t want to make things awkward but we also don’t want anyone to be upset they weren’t invited. I feel so bad my fiancé’s regretting inviting any of his cousins to begin with lol.