Welcome to DC :mickey:
If you had to do just one park, Disneyland is the simple answer. You are submurged in the magic and kids and adults will love it. You can easily spend an entire day keeping both children and all the adults happy. There are areas that the Princesses visit regularly and as mentioned before you can get the day’s schedule, Pooh and friends have a regular place to meet back in Critter Country–finding the characters at DL is not as hard as it was years ago.
I have taken a 1 year old twice to DL (two different children) and found there are lots of attractions they could enjoy with me…Small World, Pooh, Storybook Land, Dumbo, King Arthur’s Carousel, Pirates, DL Rail Road, the big riverboat, Jungle Cruise, the Tiki Room and so many more. They really enjoy the music and atmosphere. You can baby swap with the other adults on the rides the small ones cannot go on.
I wouldn’t go to only DCA, you’ll all be let down. There is a different pace in this park–it’s more mellow–but that’s not to say DCA isn’t worth some of your time if you have a 2 day hopper ticket. Soarin’ was my DD3 (at the time) favorite ride last summer, and the Electrical Parade was a major hit with both the 2yo and the 3yo, and Tritions Carousel makes for some beautiful photo opps with all the color. GoofFather mentioned a few other places to see in the park, and if it’s warm there are some places for the kiddies to get a little wet to cool off. Oh, and there is the new Monsters Inc ride, Turtle Talk with Crush and places to meet characters, but really there isn’t much for a 1yo here.
When you go to Disneyland, consider getting there at park opening and hitting Dumbo first thing (you can go back to Main Street later) and then the other rides in Fantasy Land–you can get a whole lot accomplished in that first hour or so as it can get busy there a little later in the am. Be aware that some of the rides in Fantasy Land can be a little scary as they are dark. You know your children best and they may need to warm up to them or they may just jump in.