Assuming you’re going to crop them to 1920 x 1080, your scanned image should be at least 1920 pixels x 1080 pixels or about 2 mega pixels. The file size will depend on jpg compression, but I would guess at least 1 mb.
If you have a powerful Mac, just install Windows 7 64 bit using BootCamp. You’re system already has BootCamp. I run Vegas13 on my 2010 Mac Pro and it runs very well. If you need help with the install, let me know.
I’m no expert, but personally, I’d burn it to Blu Ray. You can set the bit rate higher and produce a much better quality. BD players are cheap now and so are they burners.