I have done Holyrood twice. You will witness all kinds of outfits there but to be correct in the kilt you should wear Scottish Highland day or morning dress (not evening dress). Your dark gray Crail jacket and waistcoat should be fine but not the mess jacket which is for evening wear (after 6pm). The shirt should be plain not frilled and have a turn-down collar. White or blue should be fine. A white shirt looks a wee bit more formal. I would avoid the black tie - a bit funereal - and save the black bow tie for evening wear with the mess jacket. Any of the hose would be fine but the black would not be my favourite for day wear.

Enjoy your day with the royals.