Appropriate attire for a tombstone unveiling?

Hi all, I have been invited to a tombstone unveiling and am seeking advice on etiquette as a non Jewish person. These are the only dark outfits I have in my wardrobe at the moment, is either appropriate? I’m afraid that the first one is too tight and the second one is too short.

Also, is there any specific etiquette I should be aware of? E.g. should I bring flowers to lay at the base of the tombstone or something for the widow? Sorry for my naïveté, I respect this family a lot and want to be considerate. Thanks for any help🙂