In my view you can actually get a reasonable flavour of the landscape and wildlife of the Everglades in a day trip. The best way to do this is to either head to Shark Valley and take the tram tour or head to the Ernest F Coe Visitor Center and then to Royal Palm to walk the boardwalk, ideally in the company of a Ranger on one of their talks. If you have the time I would take two days and do both as well as heading to Everglades City to take a boat trip in the Ten Thousand Islands as this is a very different environment with different wildlife. If you are into kayaking then a longer trip would be great.