If you want a fun children's museum option check out the Kidspace Museum in Pasadena. My boys loved it as toddlers.
http://www.kidspacemuseum.org/site/P...pagename=index
We also love the California Science Center (it's free), they have a wonderful new exhibit, Ecosystems, that you could easily spend a good part of one day exploring.
http://www.californiasciencecenter.org/
the Natural History Museum is right next door to the CSC too.
AS far as the plane goes.... bring NEW little toys along.... at 2.5 my DS loved a new car we bought for him for our trip... all the doors/hood,trunk opened up.... kept him entertained for a bit. Mini pop up playsets
http://www.amazon.com/Matchbox-Pop-M.../dp/B003ZVDO3Q
Color wonder paper/books and pens
small board books
Do you have a portable DVD player? Might be worth investing in one for your trip.
Snacks were the biggest distraction. pretzels, crackers, dry cereal, raisins, fruit leathers.
Oh and The Grove has a Pottery Barn Kids store... my boys loved it when they were little with the display kitchens and puzzles etc. It's too bad they closed the FAO store... my older DS practically grew up there. All the salespeople knew us and knew my DS by name.
There is also a large park across the street, Pan Pacific Park. 3 play structures and a lot of grass and walking paths all around. we live a few blocks from the Grove so we are there often. Like someone else mentioned... go during the week to lessen the crowds.