Ideally, everyone attending will be wearing 18th century day attire.
Think “Williamsburg 1776-ish”
Ladies: While fine fabrics and costumes are always admired, it may be too hot for this type of garment, or you may not wish to subject your gowns to potential roadway oils if you are walking anywhere but on the lawn. Be advised…
Gents: Tricorn, breeches, waistcoat and coats are totally appropriate. You do not need to wear all of these if you have not yet expanded your wardrobe to include a tricorn or coat.