DVDs can be taken care of quite easily (FAVC if in Windows: see spoiler section
http://gbatemp.net/index.php?showtopic=64975 ) so I am going to ignore that part.
Video editing, I use avisynth for just about which could accomplish all you want and then some but it is a programming language which you probably do not care to learn for a quick project.
Freeware video then.
Virtualdub is OK and can do filters nicely but for anything beyond the most rudimentary cutting and pasting of clips it becomes bothersome.
Windows movie maker, I despise it but only because I find the interface clunky, the program unstable for anything slightly complex (i.e. editing more than 5 longish clips together) and the output useless (wmv is not my favourite thing and then it was not exactly good quality). If you do not care to learn anything about video editing feel free to do it as it should work.
In the end I guess I should say get a whole bunch of apps each suited to a task and use those.
For text unless it is actually on image I would say make subtitles (hardsub them if you have to)
Virtualdub is good for basic editing, grab a copy of virtualdubmpeg2 if you have a camera that is likely to output mpeg format (quite a lot of them) and virtualdubmod if you have something more exotic or have trouble opening files in the original (i.e. you use more modern codecs).
If you have to do a lot have a go just appending all the files together and chopping out the bits you do not want.
Subtitles, DVD subtitles are pictures whereas normal subtitles for the PC are text based (xml at worst). Converting between the two is not hard though (going from DVD to text is harder).
For making them:
I suggest you have a go with something from the following site:
http://www.free-codecs.com/Software/Subtitle_Tools.htm
For tweaking the output of said subtitles:
http://www.free-codecs.com/download/DVDSubEdit.htm you can do it inside already made DVDs so no need to worry there.