Mohs surgery is an excellent choice for treatment of a melanoma near the eyelid. These types of melanomas in situ (frequently called lentigo malignas) have poorly defined margins and are located in areas where preservation of healthy tissue is very important and where other types of surgery have a higher risk of recurrence.
The key is to see a Mohs surgeon with extensive experience with this type of malignancy and treatment with Mohs. These types of tumors require that the tissue be cut properly and not overfrozen, and interpretation of melanoma frozend-section slides requires that the surgeon have a great deal of experience (in other words, it is not as straight forward as some basal cell and squamous cell carcinomas). A number of Mohs surgeons use immunostains to highlight the melanoma cells more clearly. In my opinion your best option is to see a Mohs surgeon who has completed a fellowship (after residency) in Mohs surgery and is a fellow of the American College of Mohs Surgery. Talk to your potential surgeon about how they would perform Mohs surgery for melanoma and what their experience is.
Regarding cure rates, the recurrence rate for lentigo maligna (melanoma in situ on chronically sun damaged skin) through standard surgical excision (i.e. not Mohs) is historically 6-20%. That is because a standard 5 mm margin is inadequate to clear the tumor 50% of the time. The recurrence rates for this type of tumor with Mohs surgery (and the author from that particular study) is 0.3% (Greg Bricca MD, Journal of the American Academy of Dermatology, 2005) and 0% (CL Temple MD and JP Arlette MD, Journal of Surgical Oncology, 2006). There are other articles as well that look at recurrence rates for Mohs and melanoma. If you're interested and have access to the scientific literature, you could also look up articles by John A Zitelli MD on other articles regarding Mohs surgery and melanoma.
Good luck