For kid birthday parties I often print this birthday card, especially if they are getting a Lego model as a gift.
I have always printed this without supports and with a raft without any big issues.
You can customize it using the customizer tool to select a suitable size for the birthday card itself, the number of studs on the top and sides, the font size and of course the text.
I have also selected a number of google fonts that seemed appropriate for a birthday card from Google Fonts. However, if you have some nice fonts installed on your local system you can easily change the font in the openscad file if you download the file.
This is based on Andrew Sweet's Parametric Lego Brick design.