I think that is awesome idea and you should keep your son in diapers full time.
I would also recommend regular diapers such as Gentle Steps size 7 diapers if you can get them where you are or some other brand of size 7 or size 8 diapers to make him even more babyish.
Make sure he does all his pee and poop in his diapers and change him yourself.
All kids should be in diapers just like these kids.