SGD 4,000 a month should get you a very nice two or three bedroom apartment at Novena. You will have a gym, swimming pool, tennis court etc. You should be able to get something at a slightly lower price actually given the current economy.
East Coast is nice but very remote as there is no MRT around there currently. The bus network is excellent in Singapore but it would take your husband about 40-50 minutes to get to work (assuming he takes public transport) and he might have to change bus or to the tube along the way. It is by far not as convenient as Novena for him. If you will have a car it won't be much better because you will have to take CTE which is alwasy jammed during peak hours.
Just as a reminder, if you don't have a car, taking the taxi is really cheap and easy and you can be at East Cost on the weekends in no time.
One last think, keeping in mind you are Australian, the Australian School is actually in the North East near Serangoon, so Novena wouldn't be too far from that either. Come to think about it, Kovan is not too far from Ang Mo Kio either and they have a lovely condo
called Kovan Melody just next to the MRT station and a neighbourhood shopping mall (to get your groceries). You can be at Dhoby Ghaut from there within 20 mins of leaving the house and your husband should be able to catch a bus.