Cineleisure Orchard seems to be a place where my teens hang out...gaming, movies, eatries, etc. Great World City is another, although I'm not sure why, but I think it is near where some of their friends live.
Unfortunately, most expat children tend to go back to their home country during the June/July holidays to catch up with family, so not as many expat teenagers around. As the mentioned children really won't know anyone from the schools here, that makes your situation even more difficult. Check out the ages of the children in the condo
where you will be staying. Get to know them and then you will have some other children your kids ages to introduce them to and they may know of places to go or may invite them along.
Good luck, it is tough at first, but mine seem to enjoy the freedom that they get here that they won't back home!