I'll transfer this to the Video Edit forum, after a few words for starters.
For a DVD disc to be recognised properly as a DVD-Video by a standalone player, there can only be one VIDEO_TS folder on it (and strictly speaking, an AUDIO_TS folder too). Hence you will have to extract the footage from all four camera DVDs, combine them under one VIDEO_TS folder and index the different parts as chapters before burning to disc.
This is not a straightforward process, but can be made easier for someone new to camera editing and DVD authoring by using a good all-in-one application such as Ulead DVD Movie Factory. There's a month's free trial at their website here:
http://www.ulead.com/runme.htm