Hi Ally,
Just adding to the above comments and answering your queries, best to have sterling trav. cheqs. as better exchange and you can change them in a few places in Arillas, the Arillas car hire place changes all currency and has safe deposit boxes as well.
As Eileen says nearest cashpoint is Sidari ( it has been walked to,its about 3 miles) no doubt you would go to Corfu town 1 day and there is a daily bus that goes once a day, there & back.
For the Aqua park,by car or I think that the travel agents arrange trips there ?We have never been as you've got the nice Sea & Pools around Arillas, and I don't like crowds!!!!!!!!!!especially in August.
Paul/Deb5