Without exact information it's difficult to offer advice.
It sounds like you are making a documentary-style edit that incorporates both 29.97 fps "shot for TV" interlaced and 24 fps "shot on film" progressive video.
If this is the case, and your final intended output format is indeed DVD-video, then the safest bet would be as satanika suggests to keep the interlaced material as-is, and hard telecine the progressive video (i.e. apply 3:2 pulldown to convert it to 29.97 fps and encode it as interlaced).
Of course the final quality is then down to how the deinterlacer in your playback chain deals with the mixed content. I imagine the telecined stuff won't look as good as the original progressive frames, but quality should still be acceptable.