FNP does give you more options because of the ability to see patients of all age groups. In the primary care arena, the FNP would be qualified to provide care in family practice, internal medicine, pediatric, geriatric, and women's health settings. This proves that there is definitely more options if you have the broad-based training the FNP offers.
However, it doesn't mean that ANP's are useless. Remember that physicians in Internal Medicine practices only see adults and some adolescents. These kinds of practices are ideal for someone trained as an ANP. You also mentioned that you are doing a dual GNP/ANP. In my area of the country, many physician groups are constantly looking for NP's to round in long-term care facilities. If this is something you are interested in doing, then definitely seek out this type of practice and see if they are available where you live. The suggestion about rehab facilities is a good one. I worked in PM&R during my first year of being an NP in an acute rehab hospital that only admits adult patients and I was the only ACNP among the rest who all happen to be ANP's.
One of the keys to finding a job as an NP is to network early. You mentioned that you work with adults and the elderly. What kind of physicians do you get in contact with day in and day out. Could it be possible that they only treat adults and would be interested in adding a non-physician provider to their practice?
Finally, I would ask the director at U South Alabama on how easy it is to articulate to FNP after having finished your ANP. In some universities, it only takes a semester of additional credits in peds to complete the FNP component. In some, it can take longer than that. The key is to stay in the same university that will allow you to complete the FNP component in just one semester because if you take your ANP in one school and articulate to FNP in another, some of the previous courses you took may not carry over as easily. Some programs allow students to change tracks while in the program but others lock you in the specific NP track you were admitted to. I'm afraid U South Alabama might be one of those schools that lock you in the track. Again, you won't know all this information until you ask.