I have a DD4 and her all time favorite ride (we went to DL when she was 2, 3 and 4) has been consistently Haunted Mansion. She loves loves loves that ride. Next would be Dumbo. But she likes everything, I can't think of anything she doesn't like except Big Thunder, she didn't like that one at all. This time around she got to ride Star Tours and really really loved that one.
At home my daughter can not wait in lines at all, but at DL she has no problem with it. She knows she has to wait in a line to ride a ride. If she starts getting figity, it's so easy to distract them there with looking at the things around you or making a friend with the person standing in front or behind you, especially if there are kids it really helps. I see some kids playing with electronics to keep them busy.
My tips to you is: get to the park at opening, keep them well feed and hydrated, so bring lots of yummy snacks and drinks and just keep offering and offering. A yummy healthy snack can ward off any potential crashes, if you know what I mean. Take a break in the afternoon. My daughter has not napped at home in at least a year and half, at
Disneyland she naps everyday for about 2 hours. It really really really helps and is a must. Go at their pace and let them pick out rides (they love to do that).
How tall is your son? Hopefully 40" or above, we had way more fun with this height this time. So for rides, my #1 recommendation is to start out nice and slow and easy on them so he doesn't get scared at all and then is afraid to ride other things. Ride Dumbo, Casey, Storybook, the Railroad, Autopia, the carousel, Buzz, Pooh, all the nice easy not dark rides and go from there, if after a few he's not scared at all you can slowly add in Snow White or Alice kinda rides. Maybe show a couple of the YouTube video's to him beforehand. I did that with my daughter for matterhorn so she could see the big white scary monster and not be scared of him when she saw him (although she still was, but loves that ride) I hope he is a trooper and not scared. I tell you, we had so much fun this time with my daughter 40"+, we road Space together (loved it), Star Tours, Big Thunder, Splash, and all the 40+ at CAP this time, it was so fun!!!
Don't forget to check out Disney Jr. Playhouse at CAP if he likes those shows, my daughter LOVED it!!
As for the character dinning, I wouldn't try to do them all. They really do take up alot of park time I feel. It's fun, but usually once, maybe twice would be a good amount for us. You'll still hopefully see alot of characters in the parks. Let us know if you need to know where to find them and we'll all help.
Have a wonderful time!! Take lots of pics and enjoy the special time with your family