I took DS last year (then aged 6), it was a bit of a risk as I took him on his own and wasn't sure if he would brave any rides or what he would be like with the dressed up characters (they usually freak him out) but he is disney mad so thought it would be worth a try! He LOVED it. We went on nearly every ride (all the ones he was tall enough for), i was really shocked as he tries to squeeze on the tiny baby rides back home.
I got a pass and it would have been a very different holiday without one. You pick it up the first morning and they do it for the duration of your stay. The waiting times for the rides are crazy and my DS would not have gotten on a single ride without the pass!
I also took his maclaren major which was great in terms of giving him a rest, and a safe place in the crowds.
Pizza Planet is a good option for a relatively cheap meal. It's all you can eat buffet with pizzas, pastas, salads, fruits and desserts and drinks. They have a play area inside there too where DS enjoyed running free and I enjoyed a sit down. 
We stayed 3 nights at Santa Fe with a 2 day hopper pass to explore the park and studios. The santa fe is a pleasant walk away from the parks. We had breakfast in the hotel (ds enjoyed bread, cheese and juice), then had meals out. One meal at cafe mickey which was dear for the food but worth it for all the characters (it can be a bit of a scrum meeting the characters around the park and timing it to meet them).
There is a food store at the train station near the entrance of the park and studio but I never went in. I took a few bits in our cases e.g. a bag of apples, a multipack of hula hoops, etc but found we got on fine really and DS is a very picky eater.