We sent our early reader to a 1/2 day, progressive, non-academic preschool that focused on creativity and social skills too, and it worked out great. DD was a very easy going kid with a long attention span, so I also managed to get her into a class with kids one year older. The preschool seemed to attract a lot of high IQ parents, so she was not as obviously out of place as she would become in elementary school. At home, I provided plenty of books, trips to the science museum, art supplies, maps, globes, puzzles and whatever else caught her interest. It worked out really well. Don't stress too much. Many PG kids do fine in regular programs if the parents are sensitive to their needs.
