pack for Boston/beach with kids

Carry on:
umbrella stroller (gate check)
sling
backpack
(Casper little backpack for her stuff?)

include:
address book
camera, download cord, charger?
ipod?, charger? (for Casper)
DVDs for Casper (pick?)
books for Casper for plane
little toys for plane for both
snacks/dinner for both kids (check carry-on rules and see how they apply to food/baby food - is applesauce a liquid?)
bib, spoons
diapers/wipes/spare clothes
jackets? - check weather forecast
no shoes for Dillo
slip-ons for Casper (flip flops?)
copies of birth certificates

Check:
2 car seats
1 suitcase (my big)

Dillo:
diapers, wipes
shoes, couple pairs of socks
onesies for sleeps
thermometer, tylenol, suncreen, baby wash stuff
shorts/t-shirts/rompers
little bear jacket. hat?
long pants, long sleeve shirt in case it's cold
swimsuit and rash guard
needs a sun hat that fits.
extra food/snacks, bibs, little washcloths

Casper:
shampoo, Advil, non-allergic sunscreen
sneakers, sandals, flip flops
socks, underpants
pajamas (probably 2)
swimsuits (2), sun hat
shorts/t-shirts/dresses
hoodie
1-2 pair leggings in case of cold.

I am most worried about:
1. getting the car seats safely into various non-LATCH automobiles, especially under stress & time pressure (like, while everyone else is waiting in the airport parking lot).
2. getting through security checkpoint without losing the baby or my grip.
3. the fact that Dillo is almost guaranteed to stand in my lap bouncing up and down for the entire plane ride, and Casper will want an in-flight beverage that has a high percentage of being spilled. At least he'll probably be jolly and not screaming...