My suggestion would be to set your level of dress to not exceed that of the members of the wedding party itself but come in just under that level. If they are in full black tuxes then the argyll might be okay, especially when dressed down with a contrasting waistcoat---either grey or tartan. Otherwise go with the grey. You are going to stick out of the crowd anyway you look at it since you will be kilted, so no reason to go overboard with extreme formal dress. Remember, it is an event for the bride and groom, wedding party and their parents to shine, and you do not want to detract from their evening.