Bill,
No need these days to descend from the Highlands nor to even be of Scottish descent at all.
Find a common Tartan/Plaid that you like, and go with it.
You also don't need to do the "Great" Kilt for the Edwardian time period. The "Small" kilt will do just fine if a kilt is what you want.
Trousers or Knee Breaches will do just fine as well. These maybe in a plaid, or, more commonly in a wool tweed. (My father, born in Scotland, called the knee breaks "four plus fours", I'm not sure I know why?)
My best,
Blair