scan at whatever resolution you want to archive the photos...for the website use your photo software to resize the photo to 72dpi resolution and then pick the size of the image you want (in pixels: 600x400 or whatever). You'll also have the option of using more or less jpeg compression to go for the file size target you're after...I would suggest doing a "thumbnail" page of very small images which, when clicked open a page with a larger image of around 150-200kb.