I need to use a jailbroken OS on an older device (3GS), so iOS 6 is a no-go for me as well. However, as an iOS developer myself, I have written guard constructs around newer API features so that they don't cause problems with older OS versions. All you have to do is conditionally initialise your FB integration, and then don't show the FB buttons if you're unable to find the FB framework. "Feature detection" like this has been de rigeur in in-browser JS development, and is very helpful when writing apps for platforms with such a short update cycle like mobile devices.