We went to Singapore for a few days last September - girls were 2.5 and 3.5. We stayed on Sentosa Island, which I really recommend. Lots of new hotels that are seriously set up for kids. Tons to do on Sentosa and they have a really great, free monorail system to get around the island. There is the beach, aquarium, pink (yes, pink!) dolphins. Light/laser shows, interesting (for the kids too) walks etc. There is a Universal Studios on Sentosa too but we didn't go. You can take the cable car from Sentosa over the harbour and you're in Singapore downtown.

Really easy to get around with kids. The MRT is brilliant and goes just about everywhere. There are two zoos - day and night - and they're brilliant. Prices are pretty variable. There's lots of free/cheap stuff to do but also the usual overpriced entry to things like the zoo. Food is great - just about everything you could imagine. Singapore is really clean and great for things like medical treatment - always something I worry about travelling with little kids. My girls absolutely loved it and keep asking to go back.