You set the gun so they and everyone else will think they've always been whatever they turn into.
After that you wait till they sit down to rest and shoot both of them. They both become much younger, the husband shrinks almost two feet and becomes a Korean woman, well the wife grows at least two feet and turns into a black woman. You watch them for awhile and given the way there touching each other and given the fact there both still wearing wedding rings it looks like there still married.
Guess they went from being your "local happily married elderly couple" to your "local happily married interracial lesbian couple." Hope they enjoy they're new youth.