It's a great Marian Feast day with the highlight being Mass.
Plan a dinner everyone will like with a great dessert!
Take some time to discuss why it matters that Mary was immaculately conceived. She is the perfect vessel for Jesus and was made so at her very origins. See your Catechism of the Catholic Church for a better explanation.
In keeping with the service-like agenda of Advent, we treat today as , "Be Nice to Pregnant Ladies" day. We try to find a pregnant mom who needs an extra meal or help at home.