Weddingbee boards

First, keep in mind that this is not part of the ceremony.  It's not in the rubrics, but is allowed for cultural reasons (like the unity candle and using protestant vows in the US) because it is a popular practice in Latin America.  You don't have to do it as part of your ceremony, and I would highly recommend that you not do it if there are a large number of non-Catholic present (who may view it as idol worship).

First, you should only have one statue of Mary in the church, not three.  And it should be near the alter, not in the back of the church (those are requirements for how a church is laid out).  When the music plays, you take flowers, walk up to the statue of Mary, and lay down the flowers (the location of where you put the flowers depends on the church and how it's laid out - you can ask someone at the church where they go).  Keep in mind that this isn't an "offering" or a sign of adoration, it's simply a remembrance of the Blessed Virgin (much like when you place flowers at the grave site of a loved one).  Once the flowers are laid down, you pause for a second and can say a brief prayer.  After the prayer, you can bless yourself (sign of the cross) or not.  It's always acceptable to bless yourself, but it is not required. 

My church's statue of Mary is next to the alter, but she is up high.  We had a ceremony with Mass, so we just did it after communion, but we put the flower on the shelf she is standing on and then stood together and said the Hail Mary.  Our priest explained what were doing and why breifly before we did it which was nice since we had a lot of non-Catholics at the wedding.

I found a picture that shows what we did.

@starry: Most Catholic ceremonies don't have the unity candle.  There are many people who want to ban unity candles out-right because they are secular and have no place in a religious ceremony.  Some diocese have banned them, but others continue to allow it as a way to "bridge" Catholic and non-Catholic Christian tradition.

Flowers for Mary are different because that is an inherently religious act.  When you place flowers at the statue in rememberance of Mary, you're devoting you marriage to her.  Typically, that is done for people who have a particular devotion to the life of Mary. 

While this is, of course, a good thing, the issue is that it's not part of the Rite of Marriage or the Nuptial Mass.  Since both the Rite of Marriage and Nuptial Masses are considered forms of prayer, you can't just add or remove things on a whim - even if they are good things.  Adding something in the middle of the Nuptial Mass or Rite of Marriage is the same as adding something into the middle of any prayer.  Would you say the Our Father with an extra line in the middle thanking God?  Doing so would obviously not be the worst thing in the world, but that doesn't mean it's something you should do.

Someone mentioned this is particular to Hispanic churches usually. And from what I understand, that is true-- it's certainly more of a "standard" practice with Hispanic Catholics in the US, but the side of my family that traditionally does this at weddings for 3 generations at least, is actually Dutch. 

Anyway, as others have said, this is definitely a "nice to do" and not a "must do." Since you said your husband is more especially devoted to Mary, and you seem to want to do this as well, I say go for it.  But also keep in mind that just because your church usually does things a certain way (flowers to Mary, unity candle) that does not mean you *must* do it that way... Together for Life and other Catholic wedding resources can fill you in on what is in fact required, and areas where you have flexibility to do things  a little different.