Grand Hyatt is fine. It's at the crossroad junction between Orchard and Scotts Roads. It's busy till the wee hours of the morning.
Lights?
Depending on the time of the year.. you just missed Vesak Day celebrations in Little India. But there are festivals throughout the year though certain sections of Singapore tend to brighten up a bit more over religious holidays..
You may try: Orchard Road, Newton Circus (foodies paradise... take a picture of the barbequed stingray).. or Lau Pa Sat (at night only please).. Little India, Chinatown.
You have to remember that electricity is not cheap here so most office buildings are pitch black when night falls. You won't see the very lit up empty buildings like you see in North American cities.
When it's Christmas time, Orchard Road is in a slew of colours.. and when its Chinese New Year, the lights show shift to Chinatown.