I love this challenge! If you do this, PLEASE post about it! I’m always looking for new ways to improve on things.
I think the wedding & variety of locations & weather make it tricky. But, I believe anything is possible. It will depend on how extreme you want to go & if you’ll still be happy if you go that route.
Accurately weigh everything. Literally everything. Even your backpack when it’s empty. Don’t ballpark it. Ounces lead to pounds. Then decide how much you really need it (while chanting, “less is more, less is more, less is more” lol) and see if you can come up with a lighter option. People are often surprised by how heavy their clothes are. Cut the tags off your clothes. Use a Ziploc bag with all the air sucked out instead of a packing cube unless the cube is somehow lighter. Ask yourself if you really even need that.
Buy it there. Buy toiletries there or just use whatever the hotel can provide. Dentatabs instead of toothpaste. But be careful to not assume where you’re going will have “your” products & whether not having that product will affect your happiness to an unacceptable degree.
Consider thrift stores there. I’m not yet brave enough to do this but I have heard of some ultralight travelers who go thrift when they get to a place & donate when they leave so they only travel with the clothes on their back & true necessities. (I personally could see doing this with shirts, maybe even skirts. Pants? Yeah, not so much but that’s just me. Haha)
Scarves. You can get a ton of mileage out of a plain white tee with a good rotation of different lightweight scarves (that you buy there & get a good souvenir out of).
Check out Sarah Murdoch’s ultralight packing vids on YouTube. Click here
Good luck! My fingers are crossed that you update us if you even come close to achieving this.