Everyone is different in their spending, but it seems to me that if your company are willing to pay school fees then that is a big weight off your mind. We pay our own and if the company paid them for us we'd be pretty happy about it (like you, we have 2 children). They do give us a housing allowance which helps but the school fees are the biggie.
Basically we live on less than S$3,000 per month (which is more than many Singaporean people do so we are doing quite well) including utilities (cable TV and phone included in that), and we manage, but we're not exactly wealthy. We can't afford to go to expensive restaurants and the like, but we do manage a few (cheap!) trips in the region each year. Your basic wage sounds slightly more than ours so I think you will be Ok.
Like my husband says, you can live on $20 per day or $200 per day in Singapore - it just depends on your lifestyle.
With us both being families of 4 and on a similar wage I hope this helps you work out if you can afford it here. If you do manage to get the company to pay housing allowance too, I think you will be on quite a good deal. Good luck with the move.
