Your sales might slow down a bit, but I think your revenue will increase.
I had a look at your gig and if I was in your shoes I would add more value to the service. For example, do you know why people are ordering those portraits from you? Do you know the purpose?
A friend of mine is a photographer. He sells mostly nature photos. He figured out that some of his clients were using those photos to make a custom calendar. Now at the end of the year he puts together 12 of his best photos, designs them in a calendar software and sells them as downloadable products. So all the customer needs to do is download the complete set and print it out. Customers don’t need to do any tweaking unless they want to add a custom message or birthdays.
I’m not saying this would work for your gig, but I would recommend finding out if you can provide a finished product instead of a portrait.