Here are a few suggestions for your trip. I have done both WDW and DL in 2009 with our three kids, two of which are girls.
1. I encourage you to stay within walking distance of the park. Staying on site is not the necessity it is in Florida, but you want to be within walking distance or to stay at a hotel with a DEDICATED shuttle. NOT the ART or Anaheim Resort Transit.
2.Be at the parks when they open! We usually hit the security table forty to fifty minutes before offiicial park opening for DL.
3. California Adventure almost always opens the turnstiles a half an hour before their official opening time, and Soarin is up and running. So you can hit this amazing ride and be in line to head to Toy Story Mania before the park opens.
4.Getting an ADR is not NEARLY as crazy as it is for Florida, so relax. You can make your "reservations" sixty days in advance.
5. USE YOUR EARLY ENTRY which comes with all three day or longer tickets, and is also available to all people staying on site. It will let you into Fantastyland for all their NON-Fastpass rides.
6. If you want to do the Nemo Subs, but don't know if your child will freak out in a small confined space, or the line is long, walk up to the Cast Member working the rope and ask for the alternative experience. This option, an intimate room decked out to feel like a submarine with a large "viewport" shows the same effects as would be seen in the sub, but you don't get in a ship. This alternative is good for those in wheelchairs, and those who just want the alternative experience.
When the line for this cute ride is longer than 20 minutes, I would recommed the room. You will bypass all the long line and head into your climate controlled viewing room.
7. Make sure you hit these rides, as they are unique or quite different than the WDW conterparts: Matterhorn, Pirates of the Caribbean, Indiana Jones, Billy Hill and the Hillbillies(get a great ice cream sundae to share during this show), Tiki Room, Tarzan's Tree House, Sailing Ship Coumbia (especially the hold with "real" ship quarters"), Great Moments with Mr. Lincoln, Mickey's Fun Wheel, Monsters Inc., Aladdin Show, and Fantasmic. Plan plenty of time looking at New Orleans Square.
8. Check out the menus at All Ears and see what suites your family.
Have a great time!
Edited: You may want to skip Indiana Jones with a four year old. It is quite intense. It is the same ride structure as Dinosaur in Animal Kingdom, but has huge skulls, skeletons, rats, spiders, bubbling lava pit, and SNAKES. Our older daughter would have loved it as soon as she was large enough to ride, but our youngest is a much more typical "girly girl and would NOT enjoy the show." That warning also extends to Its Tough to be a Bug. It can be very intense, and if you are in doubt, seat yourself near the exit so you can leave if your daughter is overwhelmed. There is NO getting off of Indiana Jones, so I would do Bugs Life and Haunted Mansion before taking her on Indy.