How young is too young?

My partner and I don’t play any instruments and are extremely ignorant to all things guitar/lessons.

We have a 3 year old who LOVES playing a little guitar we have (he also does the same thing with a little keyboard as well). Without asking he always plays for his baby brother, he asks for us to put on songs for him to strum to, etc..

He’s such a busy kid and eventually we’d love to pay someone to give him lessons as it’s something my wife and I don’t regret picking up ourselves.

Does anyone have any advice on appropriate ages for lessons? Or even anything we could do for a young child to continue to expose them?

Thanks!