Wedding Reception???

[PiobBear]

Should I go all out or simi formal???

I was thinking Cotton hose, Kilt, white cotton shirt and vest?

That's not semi-formal, that's casual. Unless it's an explicitly casual beach or garden wedding, you might give someone the impression that either you're ignorant of the basics of etiquette, or worse, simply lack sufficient respect for your hosts to dress appropriately. While I'd wear a kilt anywhere I needed to wear clothes, I'd be very uncomfortable if I were the only guy in the room without a coat or a tie.