Display short text messages


I am looking for a simple, cheap solution to automatically display short messages to my son.
For example, I often have to go away for a short time and it would be practical if he would then, when he comes home from school somewhere find a message such as “I’ll be right back”. This could be a simple LED panel or similar.
Has anyone already implemented something like this and has a tip for me.

Thank you

with some diy and not be afraid to solder a bit…;plus have time(!)…you can conjure something up with esphome and a nextion panel or look at this below.
Other options are a old tablet with wallpanel on it (simplest imo)

ESPHome LED text notifier with basic response buttons - Share your Projects! - Home Assistant Community (home-assistant.io)

LED Matrix “On a Call” Message Sign - Share your Projects! - Home Assistant Community (home-assistant.io)

Am also interested to hear others, my main thing here is that it is never really cheap