flash is not supported on ipad/iphone .. so any facebook game wont work on devices that do not support flash.
It depends on what your boss wants the game to be.
It is possible to develop html/JS games (no need for html5) I am not sure of Android support for html5.
In any case your boss should be ready to invest a lot, depending on your target machines, you would need to acquire each and every device to do the testing because even if you use an emulator, when you release on the real thing, it is a lot slower. Not to mention that you need to target specific devices and not Android in general, a 1st Generation Android device might render your game/app slowly.
There are some Javascript based game engine (no need for html5 even) such as game query:
http://gamequery.onaluf.org/
anyways google Javascript gameengines, I am sure you will find a lot and you can then investigate what you need to be done and what you can do with each and every one.