You guys probably already heard about this, but here to remind you to check it out in case you forgot. Very lively and fun area with so many restaurants and activites.
Some parts of downtown Miami can be sketchy, I admit, but the Brickell area especially Brickell Key is very secluded and peaceful yet close to the city where so many brunch spots and even grocery stores are within a block away.
This is a really cool museum and a garden located very close to downtown Miami and a bit of a drive from South beach so I would recommend staying at a close hotel like Mandarin Oriental in Brickell Key.
I absolutely love waterparks so I had to include this. This is located inside of JW Marriott Turnberry Resort & Spa, but you don't have to stay there to get access to this waterpark. if you do stay though, you will have complimentary access.
This is the best luxury shopping mall in Miami. Even if you are not looking to buy anything, I would recommend checking it out. It's quite a fun place full of cool boutiques and large artworks.
This is my absolute favorite area of Miami as it is full of weird, funky, but super unique murals and art installations. If you're into art and design, this is the place to check out.