It's a great choice for teaching programming, IMHO. As well as the official SDK supporting C and Lua there's also a "no-code" web-based game creator called Pulp. For somebody totally new I would recommend starting with Pulp and progressing to Lua (which is very easy to read and fine for most games) and maybe even to C if they really get the bug. I've been programming for ~35 years and picked Lua so I can concentrate on my game design more than the programming. Also, developing for Playdate does not require a device — Lua/C require a computer and Pulp requires only a web browser — so it's essentially free to tryout hand at it.

Probably depends on the kids' age/ability.

The playdate sdk is Lua, which has fairly basic syntax.

However, the playdate sdk is fairly low level, so early projects will inevitably be laborious with infrequent engaging feedback cycles for kids.

They would need to be self starters with some prior programming experience, or have you slog through the annoying parts.