Re: different sources - MPEG2 wide and dv 4:3

I would keep your files as native as possible as far through the post-production chain as possible, so no: no de-interlacing. Dave's suggestion of DV is a good one.

Why would you consider de-interlacing content that was shot interlaced to begin with?

You're in a pickle here. You've got 4x3 & 16x9 content, both in SD, destined for a DVD. You either center-cut a 16x9 out of your 4x3 camera, thereby losing resolution, or your center-cut a 4x3 out of your 16x9 shot, again losing resolution. Eventually you'll have to match the 2 cameras to each other - putting out either a 16x9 or 4x3 timeline.

If the Sony card camera were HD, it would be a no-brainer to center cut 4x3 out of the 16x9 HD. If they're both SD, it comes down to a creative choice based on your compositions - can you more easily make a pleasing cut out of the 4x3 or the 16x9?