All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
In principle, a Muslim should not go to places where sins are committed unless there is a real necessity to do so, like to enjoin good and forbid evil… etc.
Allah describes His righteous Servants by Saying (what means): {And [they are] those who do not testify to falsehood, and when they pass near ill speech, they pass by with dignity.} [Quran 25:72]
So, the fact that you are not participating in this ceremony is the right thing to do as Muslims should not go to places where the two sexes intermix.
Scholars are agreed that even if Muslims should accept wedding parties' invitations, they should not participate in these parties if any sins are committed in them.
For more benefit on mixing between men and women, please refer to Fataawa 206425, 90256, 217525, 375055, and 133843.
Allah knows best.