What format are your videos on the mini-dvds? Are they individual dvd-video? (Video_TS folder containing .ifo, .bup and .vob files)
If so, you need is an authoring program that can accept them and give you a menu to select each individual video. I use DVDLab Pro, but it is expensive. There is a fully functional trial if you'd like to use it. Your input dvds must already be compliant to dvd specifications if you use this tool. Not much editing capability here though...it is primarily an authoring program.
A free authoring program one would be DVDStyler. But it cannot accept .vob files that are split. You would have to use VobMerge, or Vob2Mpeg on the dvds first, to get either one big vob for each individual video or one big mpeg2 file.
If you need to edit the files, you'll need something like VideoRedo TV Suite or Womble Mpeg Video Wizard DVD. These are not free, but both come with free trials that are fully functional. Both can accept the dvds as input, and let you edit before producing a finished dvd with a menu to select each video. You could also join videos with transitions if you like, using the Womble program. It is more versatile for that type of editing.