Well, I love me some ren faire, but I don't worry so much about "historicaly accurate" dress, If you get right down to it, 95% of folks you see dressed up at fair, the ones in kilts particularly, are not close to accurate. Or no moreso than the folks one sees dressed as fairies, Capt.Jack, bellydancers, Robin Hood or clone troopers! I just think of it as a fantasy dress-up party.
I wear one of my modern trad kilts and one of those ghillie/jacobite/pirate/whatever lace-up shirts, the rest of the kit is stuff I would wear any other day. Honestly, I would pass on the sash, it just doesn't look right to me. but your call. Likewise the weapons, I carry a sigan dubh in my hose, but dirks and swords just get heavy after a while.