There is still today, Sunday. You don´t need a car in Tigre.
Get on a train to Tigre and enjoy the beautiful ride on Train de la Costa (I think you take the train to Borges and get on this special rail there) where the train moves along the water to the beautifu delta region. There is lots to see and do when you get off the train including the entertaining mercado (fair) where you can buy last minutes Christmas presents for a fraction of what the city stores charge. Last weekend we did exactly that and I found some lovely presents for under U$10.
By the way, Tigre does mean Tiger due to the fact that if you look at the delta from above, the city is like Venice. The stripes of a tiger resemble the streets which are all water. The residents take their motor boats to town to buy their food or the large "vaporetta" launches deliver to your docks. Each house has the name the owner chose for the house (La Angelita) above the end of the dock. You can take one of the launches that serve as taxis to the residents and dor a full tour of a section. There is a wonderful restaurant called El Gato Blanco that I highly recommend. Ask the guides at the pier which of the launches goes to that section where the restaurant is.
There are a multitude of rowing clubs in Tigre also. The Argentine rowing team trains here.The architecture mostly tudor and very indicative of the British influence.
I am in Tigre today, we came yesterday afternoon (my cousin has a place here so we were sheltered from the rain). We plan to have breakfast this morning next to the mercado and do some last minute shoppping,have an asado and then return later tonight either by train or hire a remi as we brought our dog.
It will be one of the highlights of your stay in Buenos Aires. I never miss coming to Tigre.