I'd really struggle to do cabin luggage only for a week, particularly if you need a wedding outfit too. Does your flight not include a hold bag?
Check if you hotel provides beach/pool towels? even if you don't intend to swim you'll need one for a sun lounger or you might want to get in the pool just to cool off.
My packing list would be:
wedding outfit & shoes, handbag etc
underwear
PJ's / nightie (short and light)
toiletries / make up
medication
swimwear
sarong / cover-up type thing
flipflops
beach / pool towel
big pegs to clip towel to sun lounger (they're a few quid on Amazon)
sunglasses (pack them in your handbag for when you get off the plane)
sunhat
suncream
aftersun
a bag you can use to take towel, book etc down to the pool (could double up as your small item of hand luggage)
book or kindle to read by the pool / on the flight
pack of playing cards or something like Uno
crossword / puzzle book if you're into that sort of thing
ipad with something downloaded to watch on the flight and headphones
chargers for anything electronic
plug adaptor
check your mobile phone data roaming charges so you don't get stung!
a couple of dresses for the evenings or cropped trousers and a top type outfit
a couple of cardigans or sweatshirt / hoodie as it can get cool in the evenings
sandals for evenings
shorts and t-shirts / vest tops for going to breakfast in the hotel, sightseeing etc
a pair of trainers / pumps for sightseeing - wear these on the plane to travel in
a small over the shoulder or cross body bag to put your passport etc in at the airport and use in the hotel at meal times so you don't have to leave valuables on the table when you go to the buffet. Make sure it fits in your hand luggage baggage allowance though if you use it as an extra item around the airport.