High Tech Burrito is one of my favorite burrito joints. Their burritos are a great value, between $3 and $6, and I can usually make 2 meals out of them because they're HUGE!
They have all kinds of interesting flavors, such as Thai Chicken, and can be customized however you like. You can add prawns, chicken, even barbecuse sauce!
They also have a pretty good children's menu, and outdoor seating at their Oakland location. I believe they also have one on Shattuck in Berkeley.