Question About Buying A Sim Card/Phone

I am going to have to phone home twice a day while I am in Sidari for two weeks in July (for peace of mind so I can enjoy my holiday) and I am wondering if it will be cheaper for me to buy a sim card while I am there as using my EE contract phone will be extortionate!!  This is a silly question, I am planning to buy a really cheap mobile to put the sim card in and was going to get one before I go, but I not sure if the sim cards I would buy in Greece would only go in a certain type of mobile - would anyone know? Also, I am guessing I can buy sim cards in Sidari (just thought I would check). Thank you 

Have you checked whether EE may have an option for Europe travel. For instance Vodafone call it eurotraveller and I pay £2.50 per day to use my normal call, text and data usage. I did use Greek phone in the past but this is much easier as I know exactly how much I am spending each day. You only pay for the days you use.

If you and the person have a smart phone and have wifi available in your resort you could then make calls over skype or viber. 

I believe you just need you passport to register a Greek sim card. That's what I did earlier this year at Germanos in Acharavi.

I checked with EE and I get 200 talk minutes for £10 a week - sorted