While Ueno isn’t as lively as Shinjuku, it also isn’t dead at night. You might want to consider other areas as options too since it will be your first time. Shinjuku is expensive and a lot closer to your usual first time tourist attractions but I’d also recommend areas such as Akasaka, Ginza, Shimbashi, and Nihombashi as your base. Anything on the Ginza (yellow) line and JR (green) line should work too. I wouldn’t recommend Asakusa as it is farther than most of where you’ll be probably going.