Terry Pratchett for a 9 year old kid

Where to start with Terry Pratchett? Asking for a 9 year old VERY sensitive kid.

Should we try Bromeliad books - Truckers, Diggers, The Bromeliad and Wings?

My other concern - except for a sensitive kid who dislike everything dark and sad - is the language. I really want the kid to enjoy reading ad love every second of it. So the question - is 9 years old enough for Pratchett or it does make sense to wait couple of years?

Please advise! Thank you,