Congratulations on your upcoming wedding. May it be an everlasting edifice built on the foundations of Torah and mitzvot.
The union between husband and wife is truly one of holiness inasmuch as it resembles the union between G‑d and His people. Thus, your question concerning a blessing prior to consummating the marriage is apropos.
A blessing is recited under the marriage canopy before the kiddushin—the betrothal which is effected by the giving of the ring. This blessing, which thanks G‑d for sanctifying us with the mitzvah of betrothing before consummating the marriage, is recited by the rabbi who is presiding over the wedding. This blessing effectively covers the consummation of marriage as well.
Chapter 23 of Psalms is traditionally said as a prayer prior to the union between husband and wife. It is a prayer to insure that such a holy experience remains holy and pure. (Follow this link for Psalm 23.)
I hope you had the opportunity to learn about the special laws of Family Purity as they are the basis upon which sanctity is brought into the marriage and upon which Jewish families are built. Please visit your local Chabad center to arrange for the rabbi and his wife to give you and your bride private classes on this all important matter.
I hope this helps.
All the best,
Rabbi Shmuel Kogan,
Chabad.org
In your answer you stated,
"A blessing is recited under the marriage canopy before the kiddushin...This blessing, which thanks G‑d for sanctifying us with the mitzvah of betrothing before consummating the marriage..." but then you added,
"Chapter 23 of Psalms is traditionally said as a prayer prior to the union between husband and wife. It is a prayer to insure that such a holy experience remains holy and pure."
So, just to clarify, is there a different blessing (other than Chapter 23 of Psalms) that is said by the Rabbi under the chuppah? Which blessing is that?
Also, at what point prior to "the union" of husband and wife is Chapter 23 said, and by whom, and with whom present (or not present)?