One of the good ideas I came up with in discussions with my dear woman, was vitamin pills, royal jelly capsules and health tonics. To the mind of my dear woman's parents, medicine from the west is sometimes considered to be superior to that available locally. I think this is a good present because it implies a concern for their health, and the wish for their long life.
For children who are learning English, a book written in both English and Chinese may be a good idea, since it implies respect for both their language and the one they are learning. It avoids the embarrassment of giving a child a book in only English, that they are unable to understand. Similarly for an adult learning English, a book of poetry or fiction written in English and Chinese.
For children, colourful sweets, a variety of different types, is always well received. And for adults, good quality chocolate.
I do not wish to be contrary, but I think that buying cigarettes, when you yourself are a non-smoker, is not the best thing. I would not give cigarettes even to someone I disliked. I know that cigarettes would be received gratefully, but I just think that it is not such a good idea. That's my two cents on the matter.
In relation to the question of bringing food into China, I have had no problems, and heard of no-one having problems bringing in anything that is properly wrapped up.