Ah, a Hispanic or Spanish wedding. Sounds lovely.
Here is the reason behind the custom you spoke of.
After the communion and blessings the bride and groom presented a bouquet of flowers to the Virgin Mary, Our Lady of Guadalupe and guardian of the marriage, symbolizing that she would watch over the couple.
Since Our Lady and St. Joseph and Jesus are a Holy Family, asking for Mary to “watch over” the marriage is pretty logical. Who wouldn’t want to have a marriage as blessed and holy as the Virgin’s and St. Joseph’s? Who better to give an example of marriage, who better for the bride to emulate and the groom to look upon his wife as a daughter of Our Lady?
It is true that your family may not “understand” the reason for this. But I don’t understand calculus. I don’t demand that calculus “not exist”, I don’t protest that because I don’t understand it means that it is meaningless or wrong.
Or, to go even further, I obviously don’t agree with Protestantism. But I don’t get in somebody’s face, call his or her liturgy meaningless or wrong, etc. So, even if your families don’t “agree” with something at your wedding doesn’t give them a pass to criticize it. . .since YOU wouldn’t go into their church or whatever and loudly protest that the grape juice and crackers are WORTHLESS because they don’t contain the REAL PRESENCE, right?
Give them the explanation that this is a part of culture and tradition in the religious heritage you have freely chosen. They don’t HAVE to agree with it, you’re not asking them to convert, but they do have to give you the common courtesy of accepting your explanation even if they don’t agree with it, just as you do any time you walk into a non Catholic Church and see them handing out “communion”. For them, it IS communion, for us it is NOT, and that is all there is to it.
God bless you and grant you a happy marriage and loving (even if not fully understanding) in-laws.