This is a great question. Here are a few ideas. First, since it is an e-commerce business, a marketing plan should be well versed in search engine optimization techniques. This alone will be a huge step, because without this no matter how great the advertising is not many people will see the advertisements.
Second, the company can buy advertisement space on the most popular websites that deal with health. In other words, you should consider what type of websites people who are health conscious like and flood those website with your advertisements.
Third, since this is spa, you might want to consider what types of product can be sold and shipped to other places for more profits. This is important, because not everyone can come to the location. Moreover, when you cast your net further, so does your profits.
Finally, there are new companies that specifically help with marketing like, groupon, to get more people. Partnering with these companies can help tremendously with marketing.