Littlestain from my tests, the only thing that makes huge fps drop is the platform behaviour. Other collision events that i have set on the family members {checking for edgemarkers, collision with main hero etc.} are making maximum 1-2fps so far on iphone5. The platform behavior is making huge fps drop even when 5 enemies on screen.
Its very nicely visible when i have an area with no enemies or 1 enemy - it runs about 57 fps since i disabled platform behavior when family members out of screen. But from the moment when there's like 4 enemies, it goes to its knees...