Coupon or Gift Certificate - Need Advice

I'm going to run a promotion for anyone that completes an online survey created on Survey Monkey. Basically the promotion is a % off the next purchase for anyone that completes our survey.

The business rules are:

• Must be a current customer (and registered on Zen Cart).
• Only good for one purchase.
• Coupon (or certificate) is not to be redeemed by others.

We're talking about 1-2k participants in total. Does anyone have suggestions for the best/easiest way to limit redemptions to only those that complete the survey?

Would it be best to set this up as a coupon OR a gift certificate?

I'm not completely certain, but I think the customer has to purchase the gift certificate in order to generate one. I think your only option is coupons for the promotions. In any case you will have more control over the coupons. I vote coupons.

ths module could help with what you need? http://www.zen-cart.com/index.php?main_page=product_contrib_info&cPath=40_48&products_id=501