Unless the wedding invitation specifies "white tie" (and I can't imagine that it would), I'd suggest:

Douglas Kilt
Argyle Hose w/ red flashes
White fold-down collar shirt
Black "Braemar" jacketn (I'm just not a big fan of these "Eton" style jackets)
Black 3 button waistcoat
Black bowtie
Hair Sporran
Dress Sgian Dubh

Best of Luck!