This is from the USCCB's "Catholic Household Blessings and Prayers":
TABLE BLESSING FOR WEDDINGS**
This blessing may be used before the meal at a wedding reception.
A member of the wedding party or one of the parents of the newly married couple may serve as the leader.
When everyone has gathered at table and the meal is ready to be served,
all make the sign of the cross.
The minister says:
Blessed be God who has brought us together in joy.
R. Blessed be God forever.
The leader introduces the blessing in these or similar words:
We have gathered here to celebrate the love of N. and N.
God has brought them together, and we pray that God will hold them in his love always.
As the food we share will strengthen our bodies, may our time together strengthen the love that binds us.
After a time of silence, the leader prays:
Let us pray.
you sustain all creatures
and never cease to give your children the food they need.
We bless you for bringing us together
in the love that unites us around this table
where the food we take strengthens our bodies.
We pray that, nourished by your Word,
we may grow ever stronger in faith
as we strive for the coming of your Kingdom.
We ask this through Christ our Lord.