Well the offspring would definitely be oscellaris as well - no way that two oscellaris can produce a percula. And since both parents have the normal stripes, the majority of the babies will have normal stripes as well. Maybe you get lucky and get a misbar, but you won't accidentally get a snowflake. If you buy a snowflake, you won't be able to breed them - they are made sterile before being sold like most other designer clowns like picasso or lightning.
There is not much size difference in your clowns - are you sure they are a breeding pair? Not even sure if they are mated already.