HOney

you wont regret it honestly. your DS might be the type of child that grows large then shoots up like my eldest.

My second eldest weighs 22kg and I can still put a BBH on him (he's 6) I tried it once no laughing.

My DD wears them and she is 12kg and my little fella is almost 6kg and wears them

Just make sure you buy large covers though, BBH covers a great