In app purchases when transferring to a new device?

Here is my situation. My sons ipod touch is cracked so I want to transfer his data to my old iPhone 4. My hope is that I will be able to transfer all of his apps and his in app purchases over to the new device. So far I have backed up the old Ipod touch and then resored it to the iPhone. So far so good but the in app purchases have not transfered. Is there something I have missed? I just want to easily clone the one device to another.

any direction would be very welcome

Thanks