It sounds to me like the most meaningful option is to use a district tartan from the City of Edinburgh itself or one of the surrounding districts where you feel the greatest connections and comfort. While blood ties are important, most families were not clans themselves but fell under the protection of a chief and adopted his tartan or a district tartan. While there is some debate, bordering on religious disputes, on the subject of Celtic identity, I certainly believe that Celtic heritage and clan links are more about the feelings of connections and family than actual genetic or blood ties. You seem to be more tied to the land than to a chief, if so, then take the district tartan route. If you build a connection with a chief or with folks in a clan society, then it might be better to take a tartan associated with that chief or clan.