Welcome to the forum !
Although the lupus is apparently only affecting the skin, the discoid lesions are being caused by the same sort of internal autoimmune activity as other forms of lupus.
Our immune systems are producing antibodies to our own body cells. The immune system is supposed to only produce antibodies to 'foreign invaders' such as viruses and bacteria, that could harm us. It makes sense to take an oral medication that will slow down or even stop the immune system's self harming activities.
There is no way of telling whether or not the skin problems are the first sign of greater systemic involvement. Even if there are never any other symptoms of lupus, the psycho-social effects of skin disease are horrendous and if the disease is allowed to run wild, scarring could result in near total hair loss and very visible body and facial scars. That's what gave lupus its name, lupus meaning 'wolf' because they can resemble wolf or dog bites, long before anybody realised that the skin disease can be associated with artrhritis and systemic symptoms.
I suggest you and your family have a look at pictures of skin lupus linked to in a posts on Symptoms section. Worst cases are usually shown and I don't mean to scare you, but it is a fact that for some people this is the reality of untreated disease.
http://www.thelupussite.com/forum/showthread.php?t=48962
Plaquenil and other anti- malarials have been in use for over a century, on and off, for lupus. Of course they have been used for a couple hundred years for malaria prevention so there are few drugs so well understood and documented. New benefits are appearing all the time, apart from the all essential disease modifying activities. Plaquenil changes the acidic balance of the cells so new antibodies can't be formed.
If there are lesions below the neck the lupus is more likely to have systemic implications
It is fairly usual these days to treat skin lupus with medicine from the get go. However some people with maybe only a couple of lesions have found that very careful use of steroid creams and life style changes such as sun avoidance and thorough protection and stopping smoking have been enough to stop the discoid lesions.
There's nothing to stop you getting the prescription and seeing how it goes for a couple of months.
However I would strongly advise starting the Plaquenil. There should be some obvious improvement within a couple of months
Please make sure you have had thorough blood and urine tests for signs of systemic disease and continue to have them at regular intervals.
Good Luck
Clare