Employment Contract - Temporary Worker - USA Nationwide

We hire people regularly for ~2 hours a day, 10 days at a time, at locations across the USA at an hourly wage to help sell our products in stores. I need a lawyer and/or HR expert to review our contract and provide feedback / or replacement of the contract. Ideally we pay them as contractors and while we would file a 1099 for them, we would not withhold any taxes, unemployment, SS, etc. This is how we have been treating them so far anyway. If you are versed in these types of employment situations and can either A) review my contract or B) provide a standard one that you know works well in this situation then I'd like to hear from you. In your response please help me understand why you are qualified to handle this for a USA company. We are based in Oregon. I have no idea if freelancer can work for this type of thing.