Discounts can be tricky for professionals. They should be offered only occasionally, if at all. (I prefer freebies.) There’s no doubt that discounts can generate a lot of business in a short period of time, but they can also damage the perceived value of your services (or your professionalism) if done too frequently or too aggressively.
A great way to offer a discount without impairing your image, is to tie the discount to a fundraising effort.
For example, I got a discount offer from a local Lasik eye doctor: "Make a donation of $25 or more to [charity], and we’ll reduce the cost of [service] by $1,000!"
When discounts are tied to worthy causes, and seen as a special, one-time deal, not only does your reputation remain intact, you’ll be seen in a positive light, helping others in need.
I suggest you choose a charity or cause that you truly believe in, ideally, one about which you have a personal story to tell. Your personal connection to their cause will not only reinforce your "reason" for your discount, it should result in a higher response to your offer.