Daka

We have travelled with kids and used the transit hotel in Singapore airport. You can book the rooms for 6 hour blocks, definately worth it to have a bed and own bathroom! The curtains are the blackout type so it's possible to sleep at anytime. Pool is also great with a bar and towels provided. Make a reservation to be sure of getting a room.

http://www.airport-hotel.com.sg/

We also did the free bus trip into Singapore and visited a shopping centre. Got lost in shopping centre and nearly missed the bus back!

New Terminal 3 at airport is also great, plenty of quiet areas and a kids play area.