In general, these are the things I bring when traveling with my baby:
feeding paraphernalia (nursing cover, water, baby biscuits, etc.)
toiletries (baby shampoo and soap or baby top-to-toe wash, baby lotion, baby powder, baby toothbrush and baby toothpaste, baby insect repellent, baby sunblock, baby hand sanitizer)
clothes (daywear, sleepwear, swimwear)
shoes
first-aid kit
toys and books
camera
umbrella and fan
umbrella stroller
lightweight backpack
For a summer outing, aside from those I have mentioned, I never leave without my baby's floaters, beach toys, bathrobe/towel, hat and a waterproof bag that I can take along with me to the beach.
For more details, feel free to check out my blog here:
http://www.mommykay.com/travel-tips-going-away-with-a-one-year-old-things-to-bring/I also have some tips about planning an itinerary with young ones. You can read about them here:
http://www.mommykay.com/travel-tips-going-away-with-a-one-year-old-planning-your-itinerary/Hope to help other mommies with these tips.