Our kids were 4 and 16 months when we stayed in Singapore and we had a great few days.
I would recommend trying to get a hotel with a pool as this is always a big hit with the kids. Even though it was raining we still used the pool as it was so hot.
The shopping in Singapore was fantastic. The food was very good and so much choice.
Singapore airport is the best airport I have ever been too. So peaceful and clean, it didn't feel like an airport and there was so much to do for all of use.