Good morning Mel,
Thanks for getting in touch. That is correct, excursions are to paid in resort, however, what I recommend to customers, is if you do not wish to carry cash nor incur charges by taking cash out of an ATM abroad is to pop into the Post Office and get one of their Travel cards -
http://www.postoffice.co.uk/travel/travel-money/travel-money-card
this way you can take cash out of an ATM at any time without incurring charges,
I hope this helps,
Kindest,
Ben