can you find a small grains or scratch and sprinkle it in the area they spend the most time in. If you have allot of bugs and green stuff around they will probably be fine also lots of little puddles of water or shallow dishes of water. only time will tell but it sounds like the parents are...
They have plenty of down to get the job done. My geese are African thought you would get a kick out of that. They have been with the babies at 40 degree F night and done fine.
Can you give here a wind shelter her down should be able to do the rest. The babies should clime right into her wings and you gander should be offing them his warm body to. They usually dont go back to there nest with the babies. At least mine dont. Since your in South Africa what type of goose...
Once that little hatching starts talking to mama from inside the shell the whole world comes to a halt. Geese start communicating with there parents around day 18 of the hatch by rolling in the shell when they hear there parents. Is totally normal for a goose to not want or need to leave there...