How to duplicate the content of a MiniDV to a DVD?
There are a few ways to get a single large DV file imported from tape, depending on whether your constraint is budget or time:

1) QuickTime Pro 7 has a recording mode that can see DV devices. Yes, Apple still charges $29.99 for it, but the interface is simple and lets you record a long, single file. Just make sure the capture format in the app's preferences is set to 'Device Native' or something along those lines (I believe it wants to transcode to MPEG-4 by default).

2) WhackedTV was a free sample application provided by Apple to developers to demonstrate video capture frameworks. The app seems to be gone from Apple's site but a third-party mirror is available. This app lets you add a DV video/audio source, configure its capture format, and record as long as you need to. I still use this app on a regular basis.

3) A final option is to script the standard QuickTime 7 player via AppleScript to open a video capture window, which it will allow you to do even if you haven't purchased Pro. Unfortunately, I don't have the original source code for this script, so you would have to open up AppleScript Editor and QT7's dictionary and work it out through trial and error.

Any of these recording approaches will yield a .dv file (or a DV file in a .mov container), either of which can be taken in by iDVD, a simpler DVD app like Burn, or by Handbrake if you wish to transcode to MPEG-4/H.264.