Feast of, today. There is a bible story, obviously, and a mystery of the rosary, and two prayers, the Hail Mary and the Magnificat.
Also, a good time to sing the Magnificat, or Tell out my soul, or listen to Bach’s setting of the Magnificat, or anybody else’s setting of the Magnificat. The Magnificat is also generally recited in Evening prayer, if you are Catholic, or Evensong, if you are C of E.
I don’t have a suggestion for a cake. Anything suitable for travelling I suppose (travel sweet, anyone?), or for visitors. Flowers might be lilies (pinch the stamens out first, if they set you off sneezing).