A boarding pass on cream: the age as the gate number in a monospaced box, sticker rows, and the drawn rocket rising the height of the tear-off stub.
Half an A4 sheet. Two per page if your printer can do it. Your printer will ask whether to print background graphics — say yes, or the colour is what you lose. If that is more ink than you want to spend, switch to Save ink above and the design comes back as dark type on white.
The code goes to the invitation site itself, so a guest who scans it lands on the countdown, the address and the RSVP — not on an app store.
Mateo is invented and so is his party — the QR on this sheet opens the matching sample invitation. Yours carries your child’s name and links to your own invite.