At what age do we expect children to start loosing their milk teeth?

In general, the first teeth loss could be as early as 4 years old and as late as 7. And it would usually start with the lower centre teeth (as those are commonly the first to emerge). Then, there will likely be another round when the child is 5 years old and continue till all the permanent teeth have grown out (likely stop around 13 years old). Here's another article which you may find useful: http://sg.theasianparent.com/tooth-loss-in-children/