I would suggest that you draft a two year (not one year) contract.
You need to include this;
1. The company will handle all work visa issues in order to provide you with a Z-visa. You will need this in order to work in China. It will be your companies' responsibility. But you will need to assist them in doing this. You will need to apply. You will need to take the physical. You will need to collect the documentation. The company will need to pay the costs.
2. The company will provide you with a housing allowance that will assist in all living expenses for you and your family. This will cover rent, utilities, management fees,etc. For SZ, this should be around 2000 RMB (typical for a teacher) up to 10,000 (typical for an expat senior manager). Your costs will depend on who you are and what you expect. If you want to live like an American in SZ, then you will burn through money quickly. If you go local, you can save...save... save.
3. They will provide you with expat medical insurance for you and your family. There are some good resources here in expat.com that can provide this insurance for you. Just post in the forum ; "looking for expat insurance". They will contact you.
4. They will provide you with an allowance for all WORK RELATED travel expenses. There will be expenses associated with your work. Do not fall into the most common expat trap; mixing the two. Keep track of all expenses. Chances are that your boss will not understand your need for various services.
5. Airfare to and from China for you and your family.
6. A guarantee that you will get all Chinese holidays off. This will be one week off for Chinese New Year, One week off for Dragon boat festival. As well as the the few other odd holidays. You can negotiate whether or not you will be paid or not during these periods. If you do not add this, then you will be the only one working when everyone else is off. Chances are even your office building will be locked up tight as a drum and you won't be able to get in.
7. A guarantee that you can take Christmas and Christmas eve off. As well as what other American holidays that you wish to include.
8. Be careful with taxes. Have the company pay you as a 1099 instead of a W-2 employee. You will need to pay Chinese AND USA taxes.
I would advise you not to get too greedy in what you ask for. You are from the States and working for a USA based company, I would advise you this TWO TIMES. So take note. It has been my experience that most American companies have their head in the sand about other cultures and working overseas. Heck, half of them don't understand time differences.
Best of luck.