Here are some ideas, all may not pertain to an infant as young as yours, but maybe someone else could use some ideas as well... Have a great trip!
Snugli/Baby Bjorn or sling! (a must have for infants)
Stroller
Stroller accessories:
bag
cupholders
small lock to lock stroller or lock bag in stroller basket
Raincover for stroller and clips or clothes pins to attach, if needed
Sunscreen
Ziplocks
Kids Meds
Small towels to use at parks for drying off rain, fountain wetness
first aid kit
Laundry supplies
dishwashing supplies
ziplocks for ice for bottle bag
bottle bag
Bibs
Swim Diapers
Diapers
Wipes
Changing Pads
Shampoo/Body wash
tub toy
plane toys
Hats
Summer outfits
warm outfits
PJs
Socks
Bottles
Bottle bag
Bottle brush
Bathing suit
Receiving Blankets for shade/changing, etc
Crib Music/Toy
Sippy Cup
Extra padding for crib
Attaching toys and rings
Toothbrush
Jacket/Sweatshirt
Variety of jarred foods
Hi-chair/Booster for in room eating
Swim tube
sippy cups
travel garbage bags
disposable placemats
carseat
shoes/sandals
wubby (blankie)
insurance card, doctors phone number