You could transfer them onto your hard disk one at a time, and then simply copy the raw captured files onto a blank DVD. You can delete the file on the hard disk, and then repeat for each tape until they are all archived onto DVDs. When you want to edit them you can then copy the files back from the DVD(s) onto your HD, do the edits, and then create a final edited DVD at your leisure.
The files created when transferring from MiniDV to HD can be large, but make sure you capture them in the size and format you want to finally end up with (probably standard DVD?). Most capture programs will allow you to capture the video in different formats and resolution. Standard DVD resolution (720 x 480) should create a file size of approx 1GB per hour of material. I once chose to save a file in .avi format, and a 1 minute clip took up 250MB (or 15GB per hour)! Also if it is saved in DVD resolution, then many video editing programs, such as Nero, will be able to create your final edited DVDs much faster, as they do not have to re-render the video to a different resolution.