I feel like navy trousers is an obvious choice with black shoes. If it’s outdoors and during the day, perhaps going casual with footwear would be preferable, such as suede bucks, spectators or saddle shoes.
Maybe it’s just me, but I find grey jackets to be somewhat difficult to wear as odd jackets and not as versatile — perhaps made even more difficult given you’re going to a wedding instead of a more casual affair. I feel that grey is great for a full suit and for standalone trousers, but not so much up top alone. The only exception might be a more casual fabric in grey worn with dark denim.