Real world is dangerous for a baby...
From analog to digital
Seven hours later, a full vector version was born.
Ready for printing
The file is ready for printing.
Printing was ordered at diedruckerei.de . 100 postcards on 300g/m² A6 recycled paper costs ~30€ (VAT and shipping included).
The exported PDF has to be in CMYK color format. I was going to use this export plugin  before I noticed that the script actually converts the image into bitmap for CMYK transformation (it would be a disaster). Luckily, I found this other more professional solution .
Free give away!
See the reddit announcement there: https://redd.it/3m8hpt
Actually, the subreddit /r/RandomActsofCards/ is much more active than /r/PostCardExchange/. See the better cross-post here: https://redd.it/3mq192
I easily got more than 25 addresses to send my postcard to. Mostly to the USA and Canada.