I would say itti bitti aswell for chunky legs although i find my mikee magicalls are more absorbent.

Size wise i would get both, DS is 5.5 kg's and i have him in small and they will fit him for a while longer yet BUT i also put him in medium as they fit too on the tightest fitting although technically they shoudlnt yet (and ds had skinny legs).

When you buy them, try them on with a liner cause you can send them back to exchange