Just returned from our second trip to Cephalonia in 6 months & the only beach we visited was Anti Samos - we love it!  A beautiful location, absolutely stunning - obviously made famous from Captain Corelli's Mandolin.  Good number of loungers & umbrellas for €6.  There is a caravan selling any type of snack you could wish for & a taverna for meals & toilet facilities.  The beach is not tidal & swimming is very safe.  There are also some water sports to use if that takes your fancy.  The beach is pebble so probably not great for children; get some beach shoes you can swim in so you don't let the stones bet the better of you!  Definitely take a trip to Anti Samos, you will not be disappointed!!