Sail date 3/1 from Miami

Luggage Storage is the Word your looking for. Tokyo usually has lots of storage lockers and that is where i first used this at a hotel. some countries have companies that do just this, but your right to figure this out as its hard and dangerous to haul your luggage around cause there are theives who target tourists not attending to there bags. when i booked my hotel on Expedia i specifically looked to see if they offered this service. was just in Buenos Aires and checked out but had a late flight...they stored my luggage behind the desk til 8pm when i came back for it. Enjoy your travels.

I know your going to find this amusing but i do this often when i am in a country...i act like i am talking to someone as if they are listening while walking the streets touring. if i am being followed they will not know if i am alone or someone with me is nearby. look as if your not alone is what i am conveying. wave down the street and tuck into a store and look at souvenirs...bad people are looking for the easy score...make yourself aware of your surroundings.

Most Hotels, will hold onto your bags prior and even after you check out. I have done this on multiple occasions,

most recently at the Westin in downtown Chicago.

call the hotel and see if you can check in early. At least, thats my personal plan for march 10-11th. We are cruising 3/2-3/10, and staying an extra night in miami the day we debark. We also have check-in times of 4pm. But on this last day, i would really like to just relax/have a beach day at the hotel. So fingers crossed theyll let us!

Have a wonderful time. Welcome back to cruising.

Have a great time.

Thank you so much. I haven't been on a cruise in 15 years.

We have done this as well. I don’t think it’s uncommon for them to do it. Our back up plan was to rent a car so we could drive to locations we might like to see, storing the luggage in the trunk. Glad we didn’t have to do that as it was costly.

One time, we called our hotel, explained the situation, and asked if we could stop by to drop off our luggage a few hours prior to check-in (I think it was around noon). They had no problem storing it in their office behind the front counter. We went off and had a long lunch and did a little sightseeing then returned at check-in time. I'm not stating your hotel will do it, only that it worked for us, and we got the idea from someone else who had done it. It's at least worth a phone call.
Otherwise you could store the luggage at the airport, then retrieve it later in the day, although that seems to me to be a bit cumbersome. It might not bee too bad though if your hotel is near the airport and if they have a shuttle.
https://www.miami-airport.com/library/baggage-storage-rates.pdf

As for things to do in Miami, well you'll have to narrow that one down on your own.