In my opinion, no, they should not have acted differently. Sometimes people live for causes larger than their individual lives.
The cause, of course, is freedom for the Dominican Republic, freedom from the brutual dictator Trujillo. The oppression comes in many forms.
One of those forms is the abuse of women. Recall the scene in Chapter Two in which the beautiful Lina is taken as a concubine for Trujillo's pleasure. Minerva Mirabel will have none of that. She defies Trujillo at every turn, even choosing imprisonment over sexual enslavement.
Another way the Mirabels helped to change things for their country harkens back to the main theme, freedom from oppression for *all* people. They sacrifice love, deaths of their own loved ones (Papa), and their freedom in order that others might become free themselves.
Alvarez's carefully constructed novel never descends into myth. That is, the Mirabels are not saints though their actions may seem super-human. She brings the Mirabels to life with all their flaws and allows us to see how a handful of lives, not thought to be worth much, can change the world.