I consider myself an expert on Disneyland. :) Here to help.
I agree with those who've said maybe skip California Adventure this time around. Some of the best things in the park are over there (Soarin' Over Calfornia, Bug' Life movie, Muppet 3-D) but your little one is not old enough to do them yet and the rest is mostly rollercoasters. You can save a lot of money by skipping it this time.
The quality of the food at different places can change a lot over time, so check recent reviews. Try www.mouseplanet.com. A lot of websites have the menus printed so you can see pricing and items ahead of time. There is an area near Mainstreet that is a diaper changing area, with smaller bathrooms for little ones, rocking chairs etc, for if your toddler gets overwhelmed inside the park.
April is a great time of year to go because if it doesn't fall on Spring Break the park is usually pretty empty at that time. Still, be prepared to stand in lines. Try their Fast Pass system. I was skeptical about it at first but it can really help you plan out your day. It gives you a 'reservation' for that ride so you won't have to stand in the line as long and you can go see other things.
If you go to Toon Town there is a lot for smaller children there and you can take a tour of Mickey's house. Mickey is there at the end of the tour to take a picture with you.
Make sure everyone is wearing comfortable walking shoes! Bring your own water with you and have a lot of fun :)