I think you will have a pretty comfortable life on that salary. It depends of course on what kind of lifestyle you are used to... But certainly, I think you will be ok!
The Indian school has one of the more competitive pricing for school fees (Check their website for exact details) but I think it's around 6-7000 per year, per child. The other International Schools
are more than double this...
Accomodation will depend entirely on where you live. It is possible to rent a 3 BDR condo
for $1500, but then you will have to factor travel time and bus fees for your kids etc.
Is your company organising your medical insurance? It might be a good idea to have your family included in the company policy (even if you have to pay the difference if they're not covered) as it makes things easier to have everyone altogether.
We have two children also and have found that our utilities bills are about 200 SGD per month, food 6-800 per month and travel costs are max. $200. We have a very tight budget though, and make a big effort to live local style and keep costs low. On your budget, it will be impossible to own a car, have a maid and make big savings, but you will definately be able to do some of these things - just not all...
Singapore is a wonderful place for kids and families: we are very happy here. Good luck with your move!