It shouldn't be a problem stretching up your original holes, unless they're too near the edges of your earlobe. A few years ago I did exactly what you want to do, and because my holes were a bit close to the edge the piercer who helped me with stretching up advised me not to go above 2g, because if the edge of the earlobe is too thin, you can get frostbite in winter. So it depends how big you want your plugs. Good to get advice from a professional piercer. Enjoy your plugs!