Your main expenses will be the rental of a landed
property, probably 15-30k or more monthly, and Int. schools ca 60-100k annually. 2 cars and a motorbike, 2-10k monthly depending on your aspirations. Medical insurance, 10-30k annually and ca 10k monthly for anything else. mentioned or assumed. If you want a big garden, then my guess would be closer to 100k for the rental. Landed properties (i.e. semi-D or terrace houses) starts with something around 5k what has nothing that can be called a garden. Finding something reasonable (a garden that may accommodate a small "portable" swimming pool) within 10-15k may be possible but not sure how likely to happen.
From a different angle: living in Singapore is not expensive unless you have some extravagant habits, so if you would be willing to compromise on rental you can pretty much figure out the rest by yourself. Or yet differently, just factoring in some standard expanses (media, utilities, groceries, clothing etc etc), a standard upper-middle class family of 4 can easily and comfortably live on a 5-8k budget. Going out 2-3x a month to a more fancy, high end restaurant should cost you $300-700 a trip for 2 adults. This is more like an upper range. Car lease is ca 2-3k a month for some standard class, small-middle sized car.
All the rest you may figure out by yourself - use for example this site, for estimation of the rental prices. Chose the int. school and check their fees. Consider holiday destination and use some popular travel sites to estimate the costs. There are also some medical brokers sites to give you a good ideas on medical insurance. A minimum for a full coverage (almost) may start at 5k per year per person depending on the age.
