Here are three hotels located in downtown St. Pete that are less than a mile from where the civil ceremony will take place. This area is very walkable, with parks museums, restaurants, shops, bars, and the St Pete Pier all within a short distance. Please note that the reception will take place in Tampa. So you will have to travel back to St. Pete after dinner, though you will not be alone! The bride and groom live in St. Pete, as well as many other guests.
Here are two highly rated hotels in Tampa that are close to the airport. If you are flying in to attend the ceremony, or if you do not wish to drive back across the bridge to St. Pete after the reception, this location may appeal to you!
There are, of course, too many other hotels to list. However, these suggestions are highly rated, and are located near different points of interest that may appeal to your unique situation.