We used If by Rudyard Kipling and the following two:
If a child lives with tolerance,
He learns to be patient.
If a child lives with encouragement,
He learns to be confident.
If a child lives with praise,
He learns to appreciate.
If a child lives with fairness,
He learns judgement.
If a child lives with acceptance and friendship,
He learns to love the world.
I Wish for You One thing, and That is Love by William Byrd
I wish for you one thing, and that is love:
Love for life, and pure, unfettered joy
At being here upon this vivid earth.
May great pleasure come from giving pleasure,
And love that streams out from your burning heart
Light the darkened world and make it bloom.
I wish you to be loved both well and long
By all those whom you love; that these be many,
Among whom, not the least, might be yourself.
May you love the beautiful and good,
And always act with honesty and justice,
Being what you would that others be.
But most of all, I wish for you a love
Into which your love might plunge and drown,
An ocean in which you might live and breathe.
Not sure they fulfill your wish about thanks for gift of life but they may help. We also made the following dedications:
Do you both promise to love and nurture DS, to offer him stability and to give him the space to develop into his own character, making him confident and independent? (We do)
Do you both promise to care for and protect DS, for as long as he needs you. Do you promise to teach him right from wrong, honesty and integrity? (We do)
Do you both promise to always support him ? offering encouragement throughout his successes and failures, in which ever path in life he may follow? (We do)