Nick,
Sidari is the nearest town with ATM's, at the very most a 15mins drive.
As Stuart says, you will be able to exchange cash/travellers cheques in Arillas.
The road maps of Corfu are notoriosly awful, although it can be fun getting lost and 'finding' little gems of villages.
If you want a decent map, your best to buy one before you go. After reading a few recommendations I bought mine from
http://www.hellenicbookservice.com/travel/ionian.htm it cost £4.95+p&p and was published "with the co-operation of the Hellenic Army Geographical Sevice".
I have another map specifically for N.W Corfu which came with a walking guide book, I will look it out for further details when I get home this evening. I remember being quite impressed with the local details on this map.
Eating out in Arillas is very reasonable, if on a budget you can buy a 3 course meal for 7 euros! For a quick no-fuss meal Stekis Grill is very inexpensive with HUGE helpings.
'Sorry I cannot help with your Aqualand query.
Eileen.