The studios are an absolute must, in fact the last few time we've gone we've spent more time in the studios than in the Disney park
You probably want one day in Disneyland and one in the studios. The studios day is mostly shows, try and catch the first Stunt show of the day, because the stunt show is the one that runs less frequently.
Car Stunt show is an absolute must, particularly as Lightening Mcqueen is now in it. You just turn up. But as others have said it is very very cold (certainly in winter when we tend to go). If you've got a pushchair bring two blankets one to sit on one to spread over you. Or coats that cover your bottom and have hoods.
Studios: Another vote for Stitch Live and Playhouse disney. Also the stars in cars parade may well be of more interest than the Disneyland parade if you find you only have the time to do one.
Disneyland - Buzz Lightyear spin (awesome!!). Pirates of the Carribean and Phantom manor are slightly scary but awesome. If yours are keen on fast rides (and you have someone to go on them with him!!) runaway mine train and Star tours (an awesome space simulator ride).
If you're going pregnant (speaking from experience!!) Plan things well - plan the the shows so you get a good sit down at regular points during the day.
Food-wise the pizza restaurants tend to be faster service in Disney Park. Still haven't worked out a good way of doing food in the studios!! If you want to meet characters I would normally say characters meals (esp breakfast at Cafe Mickey) are a must, but frankly if your boy isn't a Mickey fan I wouldn't bother. If you do decide you want to it might be worth looking into the BBQ cookout in Disneyland cos I think Woody appears there