I for myself am making a game for iPads. I'm sizing the layout like the dimensions of the best possible resolution of the ipad3 (or whatever the newest is) and if someone plays the game on an older generation iPad it will scale down the resolution but still fill the whole screen because the devices got the same aspect ratio.
it's the same situation for iPhones older than 5.
so i guess you got to decide wheather you'll make your game for iPhone5 or for older gens. and create a second game for android and so on.
Other tip: I have made the best experiences with CocoonJS as a wrapper. i guess for now it's clearly the best amongst all the wrappers.
If you need multiple touch inputs at the same time i have a nice example for you how to deal with touchID's. (mostly needed in multiplayer games)