Debit/Credit cards are accepted everywhere should you want to make a purchase. Currency is both Turkish Lira and Euro. There's not much point in getting Turkish as you'll have to use it all. At least Euro's can be kept for another trip. The only thing you'll really need cash for is tipping. It's not something you have to do but it we generally give the very attentive waiting staff a few Euro's at the end of the evening.

Although we are All Inclusive, there will be a number of shared expenses during the trip such as beers & food at airports, tips & golf buggy hire etc. We even use it for card school winnings/losses etc. We use Splid to track these and settle up at the end of the trip so no-one is out of pocket. Download Splid from your appstore and Maz will provide the code once it is setup for the trip. 

It is illegal to gamble in public in Turkey. However, that doesn't stop Digger's card school. The Splid App can be used to track who's won / lost their holiday money without any physical cash changing hands.