Below are examples of rhymes for a first birthday card, both for a boy and a girl.
Any name can be inserted where you see James or Sarah and the rhyme remains the same.

Birthday (Boy)
Name James

The life of young James, is well on its way,
Best wishes are sent, on his first birthday.
James has shown changes, each day, and each week,
From his heart warming smile, to his first attempts to speak.
Sending Birthday wishes, to you and your son,
May you mould him, and shape him, into the man, he’ll become.

Birthday (Girl)
Name Sarah

One year ago, your world was in a spin,
Waiting for the life of your daughter to begin.
Sarah’s her name, she’s now one year old,
With her whole life ahead of her, just waiting to unfold.
Sending best wishes, on this happy day,
Sarah’s one in a million, in everyway.