Cell phones in multiple European countries? [closed]

My college-age son is traveling to Europe next month for a month-long trip, and we are trying to figure out the most straightforward way to get him cell phone access during his trip. Probably a moderate amount of text/voice/data, but not huge quantities would be needed of any of those. He lives in the USA and currently has a CDMA Android smartphone that he has through Tracfone. He will be arriving in Germany (Frankfurt), then traveling north up through Denmark, Sweden, Norway, and Iceland, before flying back to the USA.

We are looking for the easiest way for him to have cell access throughout his trip, whether that is through SIM cards in his current phone, or to just have him buy an inexpensive phone once he arrives in Germany. He will be staying in a combination of hotels and private residences on this trip, so will not have regular or reliable access to WiFi in many of his locations, so ideally would need something more than Google Voice/Hangouts or other WiFi solution. Also, he will be traveling as part of a group, so may not have the flexibility to easily wander around either the Frankfurt airport, or anywhere else in Frankfurt to find a cell phone store once he arrives.

Thanks in advance for any advice or suggestions!