She is no good at sitting still with idle time.
Runs in the family, eh?
I think she likes having purpose and helping the kids, even though she doesn't HAVE TO anymore.
I think we should all have possibilities to do this, especially since people are far healthier at 70+ than they were earlier. My day worked in some capacity all the way up to 80 - the last years it was donating his time as an art teacher to community groups.
You are also taking the investment route, so without a retirement fund, you still have a decent chance of being okay too.
Oh yes, oh yes, oh yes... I come from a long line of people who can't sit still!