Remember to direct your family with a light touch. Travelers can sometimes be strained by missed connections or crowded accommodations. Not everyone will be in a good mood during some of the picture-taking. You'll need to use a fast shutter speed to capture kids in action and other spontaneous fun. To expose your film to the correct amount of light, you should understand how shutter speed and aperture control exposure.
Aperture controls how much light strikes the film while the shutter is open.
If you have a manually adjustable camera or an automatic camera that you can use in a manual mode, experiment with different combinations of shutter speed and aperture to see what is best for the situations you expect to encounter. With ISO 64 film, increase the exposures suggested for ISO 100 film by one stop, i.e., use the next larger lens opening or the next slower shutter speed. If you stand back far enough to get all the people in, they become too small. But if you get in too close, you may cut off the people at the edges of the group. You can solve this problem by using a wide-angle lens.