Here's a Collect I wrote a few years back for use on this day.
Most gracious and gentle God, from the womb of your love you gave birth to all creation, and in your Son Jesus Christ you reveal a loving-kindness that longs to gather up your children under the shadow of your wings: Bless, we pray, all mothers, especially those who nurse and care for children. Give them patience and wisdom. Sustain them in gentleness and grace. Deepen the tenderness of their affections. Affirm them in the nobility of their calling. May our children always find in the embrace of mothers an outward and visible sign of your never-failing love and care. And through the love of our mothers, may we all feel the warmth of your tender mercies and know the constancy of your unconditional love; through Jesus Christ our Lord, who lives and reigns with you and the Holy Spirit, one God, for ever and ever. Amen.