What a terrible thing to do to "Seán". This name makes me think of a poor, urban black family, and I do not mean it as a compliment. It has no class and shows little hope of aging well.
The ''Shawn'' should rule it out for a girl, but if the name is used on males, it should at least be LEShawn, not LAShawn. So, it doesn't sound logical on either sex, and it has that trashy ghetto sound to it.