If the sun is not in the frame and you want to catch the beauty of the sky at sunset you just meter the scene directly and the scene will be rendered correctly. That means that everything which is not the sky will be rendered as a silhouette and you can exploit this if the shape is recognisable (a tree, a cactus, a windmill etc).
An example by yours truly, metering the sky "as-is":
If for any reason (such as strong sun and you don't want them to "squint") you wanted to take a picture of the kids with the sun behind them, then you could do the following:
- "Tabular exposure": with 100 ISO shade is EV 12. You cannot go much wrong if the sun is still around 20° above the horizon;
- Use of reflected light meter: meter the palm of your hand in the same shade of your kids' face, and open 1 stop.
- (best) Measure of incident light. You don't need to go near your children, there are no trees on a beach, you just turn yourself and measure incident light at your kids' face height (to keep account of light reflected by the sand) and that's the measure.
The ordinary considerations apply regarding negative film to be so forgiving that tabular exposure would most probably work very well.
* It is probably easier if you rotate the kids and place yourself between kids and sun.