Visiting Graves

Now it's OBON vacations here in Japan.
OBON is a couple of days around August 15th, which is supposed that spirits of ancestors come back from heaven to see their family.
So we take holidays in this period and go back to home town, to visit graves or to hold some Buddhist memorial services with relatives.
Our family went to graves of my father's ancestors today.
He was born in a small mountain village in Gifu prefecture.He couldn't find job there and had come to Nagoya city.Most of his relatives did so, now only few relatives are living in this village.

We cleaned graves, mowed grass, then put rice and flowers in front of graves, and chant Buddhism sutra.
My father doesn't have any sons to take over his family.2 daughters, my sister and I, both married into each husband's family, so my father's family would finish at his generation.

I wonder when my father died, who would be able to take care of these graves, which is in mountain far from our town...