What you need, is a dedicated image restauration filter that recognized the regular frequency pattern superimposed onto the prints. You can do this in advanced Image processing packages that let you compute the fourier transform of the image and then suppress or attanuate the frequency bands of the artefact with a band-stop filter.
But neither Aperture nor PhotoShop have this kind of filter. In Aperture and Photoshop you can only soften the effect by blurring and then exporting a smaller version of the image.
The algorithm that your scanner uses is probably the best that can be done, even if the resolution is only 100 dpi.
Do you still have the negatives? Scanning the negatives at a high resolution may give you better results.