If you raise the children to be served, they will grow up with that expectation, and will not learn how to make their own food. They will go into the kitchen and get their favorite foods, such a cookies or crackers, but they will not make dinner. For example, a teenage boy with Aspergers and his older brother were left by the parents for the day. He was hungry, but did not eat anything until his brother came home and opened a can of beans and warmed it up. When asked why he did not get the beans for himself, he said he was waiting for the brother to come home. This young man had language, and was mainstreamed academically, but did not have the life skills and the expectation of doing things for himself.
In teaching food preparation, check with the parents, and make sure that the same skill is practiced at home and at your house. Start with the child’s favorite cooked food to increase interest and motivation. Make picture schedules for what comes first and second. Repeat the teaching over many times, in the same sequence. I found really good videos on YouTube of cooking and redirecting: