Bill,
I use the same scanner for my 35mm negatives and slides. I find it useful to make my scans at the maximum possible resolution, which does indeed create a file of approximately 64MB.
I then crop and resize the image from within Photoshop to the desired size and resolution for printing.
I have standardized on 300dpi for printing as it seems to work well with my printers.
I believe the Nikon Scan software makes it possible to create the output file at the final size and dpi you wish, although I have not used it this way.
By my math, which is frequently suspect, you could achieve a final 4×6 inch output file at 300dpi by scanning your 35mm negative at approximately 1200dpi.
Good Luck