Bichon Barb: I have done the long haul South Pacific trip many times.
One question: is there a specific reason you are travelling to Europe, then Singapore, then to Malaysian? I would actually suggest looking into going west to get east. It's much easier on you where jet-lag is concerned and the timing for your body clock is better.
It is also much easier to travel on long flights when it is dark.
Most Asia/Pacific flights leave in the early evening. You get dinner, then the first of two or three movies come on (by now the sun has set) and you fly throughout the night. You have been up all day, so your body clock says it's time to sleep, which is what most people do. Get your kids up early the day you leave, and by the time they get on the plane they will be tired. The game boys and DVD players work well, but as mentioned previously try to book an airline that has seatback TV's (I believe Singapore Airlines does) Some even have electronic games, so ask your
travel agent or check the airlines website for amenities on board. A few hours before arrival, the flight attendants wake you up to prepare you for breakfast. You eat, they clean up and you are there!
The more direct flight the better. Each additional stop or change of planes will make it harder for you and the kids.
Make sure they drink lots of water (not soda) on board to keep them hydrated (and happy!)
Another tip, once you arrive you will be very tired, try to stay up the remainder on the day. Have an early dinner and go to bed around the same time as you normally do. This is the hardest part, and your kids will probably want to sleep before, but if you are able to stay up and get your regular nights sleep, you will be OK to start the next day on schedule.
Have a great trip!