Currently, there is no such thing as a show quality Lavender Orpington. They are still a project bird. Ours are Splits and are producing some very good quality Self Blue chicks. PM me if we can help your son. (We are a sucker for kids).
If the chicks look buff, then they are most likely a cross with buffs. Several on eBay have been listing this. Though we do list on eBay, it is always best to buy from a breeder you know and trust. Our chicks hatch out Black, Black split to Self Blue, and Self Blue. If they sold you "Lavender" then they should be hatching out 100% Self Blue.
If the chicks look buff, then they are most likely a cross with buffs. Several on eBay have been listing this. Though we do list on eBay, it is always best to buy from a breeder you know and trust. Our chicks hatch out Black, Black split to Self Blue, and Self Blue. If they sold you "Lavender" then they should be hatching out 100% Self Blue.