Write the card, take the link, send it. There are no accounts, nothing is saved anywhere, and it costs nothing, ever.
Questions
Is it really free?
Yes, completely. No accounts, no adverts, nothing to pay, ever. The whole thing is a single file on a web server.
Is anything stored about my child?
No. Everything you type goes into the link itself, after the #, and browsers never send that part to any server. There is no database, no cookies and no tracking.
Which languages does it work in?
Eleven: English, हिन्दी, বাংলা, தமிழ், Español, Português, Français, Deutsch, العربية, 中文 and 日本語.
Do I need to install anything?
No. It opens in any browser and works on phones. You can also save it as a file and open it later with no internet at all.
Can I make a party invitation too?
Yes. Pick Invitation at the top: you add the day, the time, the place and a phone number or an email address, and your guests get a card with a reply button that opens their own messages or mail. Same link, same privacy.