It does look very nice.

With a PC style jacket you are giving a VERY formal appearance. If your Christmas Luncheon is anything like ours, you will be WAY over-dressed. That's OK, but if you are going to take it to that level, it needs to be done appropriately. That being said.

Is your Day sporran Black? If so, I'd opt for the black sporran and match it with some black shoes and hose.

Hose can get by with cream but to balance the outfit I'd go with black or Green to match the kilt.

You may consider dressing it down and only wear the vest. Without silver buttons it will give a dressy but casual appearance and eliminate the need to formailse many of the other features.

If you want to wear the brown sporran, I'd opt for a brownish sweater to help tie the sporran to the outfit. Add brown shoes and you'll look great.

Just my opinioin.