You should definitely visit Montevideo. Take minimum 4 days, ideally Thursday to Sunday. Tons of things to do, especially February to mid December.
Most museums in Montevideo are run by the state and free to visit. The Gaucho Museum is located in a fantastic “palacio” worth a visit in its own right.
My favourite park in Montevideo, Parque Rodo has tons of stuff to do for adults and children alike and the best view of the sunset in the city.