Senan,
I suppose the first step would be to nail down some specific requirements.
The easiest way would probably be to buy one or more low cost e-bay EL supplies to determine what voltage you actually need to get the required brightness from the specific EL panel you are planning to use.
Published specifications cannot be relied upon, only you will know how bright it needs to be once you see it working.
Brightness requirements vary a lot, and so does panel size and colour, so its a fairly important initial step.