I think the easiest route is to let a transfer service create the DVD for you. I would use a local service if possible. Super8 film tends to be irreplaceable as you don't have backups, so personally, prefer to transfer them myself.
Sony Vegas editor will allow you to edit the DVD's VOB video files directly, which are really just Mpeg 2 files. No need to convert these first. Just transfer the DVD to your hard drive, then drag and drop the VOB files directly into Vegas timeline. You can download and use any version of Vegas for 30 days free from Sony's website. You can also buy some versions of Vegas Movie Studio on Amazon for around $25.
Otherwise, there are a number of free media conversion apps that can convert the DVD over to other media formats for use on portable devices.