You can convert the DivX file to VOB (which is the format used by DVDs). Then, using your DVD authoring software, recreate the menu. This way you can have a relevant screenshot or image for each menu item and change the titles if required.
As they are valuable family videos, I recommend you make several copies of the original master DivX file and the newly created DVD, and store them in a cool, dark place.
EDIT: You might find this
Convert a DivX or XviD AVI to DVD useful, if a little complicated. There are probably easier methods, so hang on for some more replies from our video experts.