Length and color of tie.

[UmAnOnion]

I would suggest if you can't get a tie in the same tartan as your kilt, then a black tie would be appropriate for this sort of occasion. Tie should come down to top of waistbelt of kilt.

Chac, Sorry to hear about your grandfather - sounds like he as a very good man.
I would think the widest part of the tie should be at the same level as the top of the waistband of the kilt - same as when wearing trousers {shudder}
If it's any higher the tie point will emphasize any belly issues the wearer might have and look odd. ??: