Plaza Serrano is the local name for Plaza Julio Cortazar (one of Argentina's most famous authors). There are many bars, clubs, and restaurants lining this plaza. That being said, it's also family friendly during the day, as there is a playground in the middle of the plaza. If you're into souvenirs, artisans and knick-knacks, I recommend the fair on weekends and holidays, where locals sell really cool items. Buenos Aires is very laid back and you will find that many bars and restaurants let you drink outside, which is really great during Argentine summers. Though Plaza Serrano does get overrun by tourists (which makes the price of items go up) there are many great happy hours during the week that you can take advantage of.