it's very strange. I never heard any Chinese couple have done that before . But you can do it if you feel like to ！it's really sweet and I bet they will like the cards.

You need to make up little gift packages of happiness candies or chocolates and give them to each guest as they leave your reception dinner. You can include a little thank you message in these, but you don't have to send out letters after the wedding day.

Even if sending out letters of thanks after the wedding day is not traditional in China, do it if you feel it is the right thing for you to do. Don't disregard any of your traditions, especially if it is one of courtesy.

It has not happened after any of the weddings I have participated in. I think it is a nice gesture, go for it and spread your culture (and my culture) 

I did it for the guests that came from abroad.  Now finding thank you cards is a whole different story.  Usually Chinese keep a list of how much they received from each guest for future reference.  They keep this list for years and will repay the same amount in the future-plus inflation. 

I don't think they give you post wedding cards here. You get the red envelopes at the beginning and that's about it as far as cards or anything in an envelope goes..