Marlyn,
The locals flee the city in January and Febraury (to the local beaches, Uruguay, to the countryside, or whatever you are able to afford), so you won't find any major party.
If you are staying in Recoleta, you can have a good time in any of the hotels along Posadas , Four Seasons, Ceasar, Duhau Park, and Alvear. For the fireworks , don't bother even the few portenios who stay will begin "disturbing" with the ""canitas" and "petardos" let's say on the 26th. so before your arrival we''ll be gratefully enjoying a concert for free.
Anwyway, should there be a party, I doubt you would enjoy it, and I don't want to be an "aguafiesstas". Our concept of enjoyment differs very much from the anglosaxon. Normally the events are so crowded people have to push each other to greet, make it from one place to another, or go to the toilet. The music is so loud you don't hear each other so you need to yell, to get passed the security everybody bumps and pushes because many who have not been invited want to get in....
Weddings is another issue. I have never been to an american one, but here the bridesmaid gets thrown to the air, their parents as well, there are not any speeches once again the music is so loud that if you happen to be seated near the speakers? or waffles? you feel auditively impaired. Then everything starts around 10 pm. But you get used to this, I wonder if I could enjoy at this point in time somthing different.
I don't know what happens with New Years Eve starting time, I guess with so many tourists they must have changed it since americans have dinner at 7 (we argentines have tea at that time)
Have a good time!