I would be careful with the Sharpie. Although they're labeled as 'non toxic' for children to use, there can be harmful effects for large areas and/or extended use and repeated application. Although a small, not really covering mark should be fine. I remember attending one game where someone covered a third of his face with sharpie and within an hour was suffering from headaches and nausea.
I believe that there are some alcohol based makeup pens out there that work just like sharpies but are meant to put designs that last onto skin. They will cost a bit more ($10-15 per pen) but if you plan on using it long term, I'd suggest looking into it.