A small word from the little one...

Present him with some flowers and slip in a card. On this, paste a small picture of the ultrasound scan on the front, and you write on the back of the card the following:

"Hello,
This little word to tell you that I decided to invite me to your next Christmas Eve (24th), or on the anniversary of my big brother (17th) and even on the birthday of my mom (13th )! We haven't met yet, I am 1-7 months and my name is XX or XY! 
 See you soon! "

Another idea
"Hi! PROVISIONAL My name is Little One, I am 15 weeks, I'm not completely finished yet. But I will be on..."