Here is what our kitchen table looks like for this Solemnity of the Annunciation of the Angel Gabriel to Our Lady:
The image is of Our Lady of Guadalupe, and I have this frame and the vase of flowers sitting above my kitchen sink at all times to remind me to be humble and gracious in my daily life. The idea for the candle with the image of the baby Jesus inside came from here, and the cake is just a simple yellow cake with "Yes!" written on top, to remind us of Mary's "yes" to God.
And just a brief caveat: If all you have done today is explain to your children the significance of this Solemnity, then don't worry about it, that's enough! Maybe add in an Angelus for mealtime or say a decade of the Rosary, but the rest is just icing on the cake :)