I agree with mlpgd. Nobody should know what your inlaws will expect more than their own daughter. It’s best to ask her. You have this going for you: Whether her parents are intractably traditional or amazingly open-minded, they will definitely expect you and your own culture to be very different from what they’re used to. Be prepared to have your fiancee smooth away any misunderstandings.
The Chinese are a very social lot, and if, say, you’re on an outing or even in your home and you go and get a snack for yourself (very normal and accepted in the West), it’s considered rude if you don’t offer something to the others.
In my experience, most Chinese are not very adventurous when it comes to new foods. This is why Chinese tour groups in other countries tend to still eat at Chinese restaurants. So, as another poster stated, it would be appreciated if you could provide them with Chinese food at first, and then later try succesting something different once they’ve settled in.
Also as stated above, always pour tea in other people’s cups - eldest first - before you pour your own.
You will be expected to show them around: a visit to tourist attractions, shopping for souvenirs, a short hike to a waterfall, etc. And you will be taking photos of various family members standing in various permutations in front of famous tourist sites. If you take a picture without a person in it, they might be puzzled.
As the host, it is your position to pay most of the time. They may very well pay at some point, but do not let this take place until near the end of their visit. If they do offer to pay, refuse their offer at least three times. If they continue to insist, accept their offer grudgingly and promise to treat the next time.
When drinking alcohol at a sit-down meal (including beer), always offer a toast to the others before taking a sip. If you want to really impress them, open up a bottle of XO cognac or expensive scotch.
Try to initiate a toast (“jing4 jiu3” in Mandarin) to your future parents-in-law at some point early in each sit-down meal. Your fiancee should be able to show you how to carry out such a toast. Example: “I’d like to make a toast to you, my future parents in law.” Lift your cup with both hands and hold it up to each of them. They’ll do the same. Then drink, then hold your cup up again with both hands. It’s considered the highest respect if you drain your glass and show them the empty glass, but this might lead to more glass-draining! Glasses are not clinked in customary Chinese toasts.
After the wedding, you will be part of the family. You will be expected to call your parents “Mama” and “Baba” or whatever colloquial equivalent they prefer. Do not use their names. (Actually, I don’t even know the real names of most of my wife’s relatives!) You can address your fiancee’s siblings, cousins, nieces, nephews etc. by their names, but not anyone on the older generation, whom you address using the complex relationship terminology that can confuse even the Chinese! Examples: “2nd maternal uncle” or “husband of eldest paternal aunt”!
No idea about the money - dowries, brideprices, etc. I’ve never had to worry about it. I got married in Taiwan, and all details about the wedding plans were handled by my now mother-in-law. I had no say at all, so I just sat back and let her do all the work.
Hope this helps.