When our little one was born, we printed the relevant information on the A6 sheet and, using permanent Pritt glue, glued it in the centre of the A4 sheet, covering the magnet.
And with that, the birth announcement card was complete.
The practical side: With the exception of the A6 sheet, we were able to prepare everything in advance.
It kept us busy every evening for one week.
One small disadvantage: The magnet we used is a little bit too strong and the cards kept sticking together.
But it was no problem to separate them and it did not damage the cards.