Pampers Splashers Singles - order just enough for your trip. 

Pampers Splashers swim pants have a snug fit and won't swell up in water like regular diapers.  Comes with Dora, Elmo, and Spiderman prints.  

Size Small, Size 3-4, fits 16-34 pounds

Size Medium, Size 5, fits 30-40 pounds 

Size Large, Size 6, fits 37+ pounds