How is the family changed by the guest's arrival in "The Ambitious Guest" by Nathaniel Hawthorne?

It is important to note the way that Hawthorne
deliberately presents the family in this excellent story as being very happy and
contented together, in spite of the storm outside and the threatening mountain that
looms over them. Consider the way Hawthorne presents the family to
us:

The faces
of the father and mother had a sober gladness; the children laughed; the eldest daughter
was the image of Happiness at seventeen; and the aged grandmother, who sat knitting in
the warmest place, was the image of Happiness grown old. They had found the "herb,
heartsease," in the bleakest spot of all New
England.

Note how all of the
family are presented as being perfectly contented with their lot. However, the arrival
of the guest with his wide and far-ranging ambitions changes of all of this. He causes
each of the family in turn to consider how they will be remembered and what acts will
commemorate their life. An important quote comes just before the landslide that kills
them all:

"Old
and young, we dream of graves and monuments," murmured the stranger
youth.

The arrival of the
guest therefore causes the family members to become unhappy with their lot in life and
to begin to consider what their life amounts to. The irony is of course that by leaving
their house, the place of their contentment, they actually all die. However, it is the
family that is remembered and the guest, with all of his ambitions, that is forgotten.
Hawthorne seems to be suggesting it is better to live a quiet and happy life than to
seek to leave your mark on the world.