I would suggest calling her uncle and saying: "Happy birthday! Unfortunately, I cannot make it tonight. I have plans, but wanted to let you know I appreciate you and the invitation."
^^^^This is how to DB^^^^
"What is best for my kids is best for me" Amor Fati Link to quotes: https://www.divorcebusting.com/forums/ubbthreads.php?ubb=showflat&Number=2879712