So I made it back from Vegas in one piece, and am debating a full post about it. Until I decide, let me just say packing-wise I did pretty well, so thanks for the advice, everyone! The only things I didn't end up using (laughably) were the damn hiking boots and yoga mat/clothes, as we hardly left the hotel and didn't need my gear for yoga at the hotel. So leaving them out would have made it about 68% easier to pack but oh well.
All articles of cute, summery and dressy clothing did get worn except one (spare dressy skirt = overkill) and the only think I wish I had had was more fun jewelry (I went light there and regretted it in retrospect) as it makes it more fun to dress up similar outfits differently. I brought mid-sized stuff and now wish I had gone all out.
So thanks again for the tips, everybody! I love packing for a trip because it means I can just bring all my very favorite stuff and forget about the other 80% of my wardrobe. I would say this was a good strategy for figuring out what to cull in my wardrobe in general but I think it's really more that there are just certain things that I should buy three at a time. For example, everything I packed.