少し原文にない英文を入れました。赤ちゃんが生まれると、"An addition to the Rurarurara family" というメッセージを入れたカードが送られて来るので、"a soon-to-be addition"と書き出しで使いました。
Congratulation on a soon-to-be addition to your family.
I can guaranty that your baby will be a tall one like both of you are!
Take a good care of yourself during pregnancy. We are all praying that you will have the healthiest baby that you've ever seen.
Let's go on a "hanami" trip after the baby is born!
with love and hugs