My parents are using tracfone here in the us. From my understanding they will not work in Germany. What would be the cheapest and easiest option for them to have a phone to keep in touch with me while we are in germany for 10 days?

they never used a smartphone in their whole life and think they would have a hard time with a spare unlocked iphone 5s

My wife and I use tombile and I know it will work in germany