You can wear anything there! You'll see loads of Californians who are wearing their shorts, t-shirts and flipflops, then people who go glitzy just for the fun of it. Too much air-conditioning everywhere.
For hiking, bring stuff to cover up if sun is an issue for you. It's bright out here in the desert in the spring and people get burnt without even realizing it because the air is so dry you don't notice the heat as much. Hat and bottled water are essential, even for a short hike. Dehydration is what kills people, and even a little can give a headache that is no fun.
Comfortable shoes if you want to walk the strip. Something warm for night if you want to walkabout and watch the crowds. Once the sun goes down it cools off fast and then spring can be windy.
Husband might want a jacket for dinner if you plan to go to one of the celebrity restaurants.
What happens in Vegas stays in Vegas, and no one will bat an eye regardless, so it's a chance to have bring out the fun clothes. Lotsa shopping in the casinos if you want. Congrats on your anniversary.
