Growing up from northeast of China, I am used to eating dumplings and finding out the coins in dumplings on Spring Festival Eve as a symbol of good wish.
^The parallelism here is weak and affects the overall quality of the sentence. Revise.
Since this is a new paragraph, I would specify who "we" is.
^Good point. Although we as readers can understand that you are referring to the family you stayed with, perhaps you should specify who you asked, since that in effect would give more detail and life to the essay.
thoughtknew that some Chinese famil yies would not eat dumplings on the Spring Festival Eve until they told me it's not the tradition of people living in the south.
^Who is 'they'?
However, they told me they loved to make dumplings with me.
^Did you make dumplings with them before? If not, then be aware that this is what your sentence suggests.
Dumplings I made were bigger with more meat, they made smaller with more vegetables, just like people in the north are forthright and uninhibited, while people in the south are tender and discreet. Although they look different, even taste different, they together made a delicate dish.
^I do not get the bigger with meat and smaller with vegetables simile.
It may be a compliment to be compared with the image of strength and a group of alpha males/females, but it can be quite degrading to compare someone with a frail and small vegetable.
Also, I do not see how you can compare being forthright with being tender, and uninhibited with being discreet. Neither of these are comparable to each other.