Zip Lock baggies... various sizes. Sandwich size for keeping things in fanny pack dry, gallon size for holding shampoo and other items that may spill - averts a disaster.
Change - both for the laundry machines and for the penny presses. I also bring an empty film canister to carry some quarters and a few pennies in... to the parks for the penny presses.
Individual packets of laundry soap and dryer sheets (zip lock baggies work great for this too!). A laundry bag is useful too. Doing laundry is very easy during afternoon swim breaks (as the facilities are adjacent to the pools)... and keeps everyone in their favorite clothes - while reducing what you need to pack.
A fully stocked "family medicine cabinet" bag. I have a small nylon bag I keep these supplies in... and it is kept stocked... so I take it with us on every trip. Items included are:
Advil/Tylenol
Sudafed/Benadryl
Bonine/Dramamine
Immodium
Antiseptic spray
Aloe Gel for sunburns
Bandaids
Small sewing kit with scissors
Moleskin and foot soak packets
Neosporin
Cortisone Cream
Tums
Pepto Bismol Tablets
Insect repellent
Safe Sea w/Sunscreen (cruise)
Small sport wallet with only the essentials. Drivers License, cash, travelers checks, credit cards I plan to use, medical insurance info, and emergency phone numbers. Everything else - STAYS HOME.
In a separate bag... a copy of all the important documents in your wallet... the travelers checks, the drivers license, medical cards etc. Front and back... as you would need this info if anything were stolen or lost.
Small collapsible cooler for your room - get ice in one of the Gallon sized ziplock baggies and use this to hold small cartons of milk and fruit etc... for quick breakfast's on your early morning schedules.
Two pairs of very comfortable walking shoes. Rotate shoes every day.
More money then you budget to spend. You will invariably need it.
Your sense of wonder and excitement! Have a great trip!