I don't know how Winavi merge files, but are they all in one VTS?
I think it is easier to do all this in
DVDLab. You can import the Winavi files into the DVDLab asset bin (all demuxed into elementary streams) and then into the Movie section, with defined chapters. With the menu created, you can have the number of created buttons to link to the movie chapters.
With the
DvdReMake approach, adjustment of some commands from First Play is necessary to point to the imported menu, whether it is in VMG or VTSM domain. So the DVDLab approach is easier as it routes everything for you.