Video resizing

[Mattaut]

I have some clips that I need to edit then burn to DVD and most of them are 640x480. I have already converted most of them to either DV or QT AIC at 640x480 and have started editing them, but I just realized that they will need to have bigger dimensions as they will be played full screen on a TV. Which option would be best for video quality?
1. Go back and re-convert all of them with the proper dimensions
2. Keep editing and when I export them from iMovie set the proper dimensions
3. Export them at 640x480, then when they are played expand it to fit the screen.

Thanks

 

[spinnerlys]

What is the original resolution of the original video clips?

Do you want to make an NTSC or PAL DVD?

Do want to keep the 4:3 aspect ratio?

 

[Mattaut]

What is the original resolution of the original video clips?

Do you want to make an NTSC or PAL DVD?

Do want to keep the 4:3 aspect ratio?

Some are 640x480 and some are 720x480, though when I set the output for the 720x480 to the same dimensions it looks stretched so I set it to 640x480 and it looks normal.
NTSC
I would like to keep it 4:3 so it doesn't look stretched and have letterbox on the left and right sides.