This will be my third St Patricks day here, and the "entertainment" varies.
Reconquista and the partying are definitely NOT for children - It's an excuse for locals to get drunk, and for some reason pretend to be Irish for the day - I haven't worked out why yet.
Last year we went to Plaza Irlanda, where there was a short ceremony, then the Ambassador and local dignities went to a Church Service, and there was a festival planned on the Plaza. Unfortunately the heavens opened up, and everyone had to retire to the Beer tent and the festival had to be cancelled. Later in the evening we went to CasaBar, where everyone was enjoying the "holiday", with face paints etc...
Usually the embassy sends out details of the "official" ceremonies, and as soon as I have them I will post the details for you.