not flown with Malaysia, but with Singapore (as recently as last week) the stroller goes with you to the gate, staff then take it and if you stop for refulling, tough, but a change of plane and you get the stroller back as you come off the plane, then go through the same procedure for your next plane. At Adelaide it will come through with the luggage NOT to the plane door, so a carrier is a good idea for that time.
Worst case, most airports do have stollers for loan too.
It is a good idea to reserve seats, but remember until you check in, they are not guaranteed, cos someone may come along with a priority need that takes the seats you had reserved. It doesn't happen often, but in the past, I have even been moved once issued with a boarding pass!
EDIT: remember you can book a child meal for the kids too.
and security should just make you taste each milk bottle for your bubs I reckon. I bought those ready milk cartons one time, and they made me open and taste all of them! you could buy them through the screening at Boots, but couldn't be guaranteed they would have what you wanted