Sorry for the late reply guys
Right. The HAF has officially announced that all bases will be open for 4 days; Saturday 8th, Sunday 9th, Monday 10th, Tuesday 11th. According to the same official announcement visiting hours will be from 0900 to 1700 except for Saturday 8th where the bases will open at 1300. (Sunset is at approx. 1715)
Photography is allowed only for the static display. Having said that you may find that the individual base security officer on duty the day and time you are visiting thinks otherwise. That is a possibility.
The only flying display announced will happen at Tatoi - Dekelia AB at 1300 hours during the weekend. Notice that on Saturday the time of the display is the same with the gate open time. This display should (usually) consist of a CL415 water drop, a T-6A solo demo and a HAF Super Puma CSAR demo.
For the rest of the bases, you should expect no flying but there should be a variety of visiting aircraft from other bases. For example when visiting Andravida AB you should expect to see an A-7 and a Mirage 2000 and maybe an F-16, a T-2, etc in addition to the resident Phantoms.
It is practically possible to visit more than two bases in one day. For example you can do Kalamata, Andravida and Araxos on the same day. Also Eleysina, Tatoi - Dekelia and Tanagra. Then Nea Anhialos, Larisa, Mikra, Sedes. Off the beaten track (and for good reason) is Tripoli AB with a small collection of preserved aircraft and maybe a visiting type, Agrinion AB with retired - preserved aircraft but only a handful would be photographable, Preveza - Aktion AB with visiting types but very far from the rest of the bases.
General advise. Gate guard aircraft are usually off limits. Aircraft dumps are also usually off limits. Ask before taking a picture just to be on the safe side or make prior arrangements with the HAF HQ.
Should you have any more questions I'll be glad to answer them. Also, members of the Hellenic Aviation Enthusiasts Society "Air-Born" will be out and about during those days. We may be able to help you on the spot
HTH