Where would you go at night if you had 2 days in Tokyo (after going to 1 day in Tokyo Disneyland and the other in DisneySea)

You won't have much time and energy left after spending full day in DisneyLand or DisneySea. Normally people stay until night to see parades and shows. They close at 22:00. You can buy souvenirs in Disney shop in front of Maihama station, which is open until 23:00. Then take train back to Tokyo station, unless you stay at Disney hotel. 

If I am a tourist, I simply eat dinner around Tokyo station and rest at hotel. There are some restaurants in Tokyo station. I recommend ramen street.

I'd go to the places that interest me. Which may be different than what interests you.

Try looking through the JNTO Tokyo Page, or Japan Guide, or the official city tourist page to get some ideas. Some night city views can be nice, but places like the Sky Tree are expensive. There are however many other places that are free.

I haven't been myself , but from what i've read and from what i'm planning myself I would say check out the Skytree at night time and look at the view. Also if you want a more nightlife vibe hit up shinjuku and go bar hopping.