Did a couple of AWESOME day trips on the last FT Cow Do, in BsAs over Labor Day.
Did the Colonia/Uraguary one...excellent. Great way to chill out wandering around the historic city, taking in the view from the top of the lighthouse, enjoying a casual lunch, just wandering. Plenty of ferry times for depatures/returns on the Boquebus.
Did the estancia option: the Estancia Los Dos Hermanos. Ana & Pancho are THE BEST!! And, they picked us up at our hotels & dropped us off at the EZE airport in time for our flights back. Can't say enough good things about the day there, how cheap it was, the incredible value it was for all that one got for the money, & the convenience.