Okay, so after copying content to the mother article, I blank the page on each sub-article and replace what was there with #REDIRECT [[article name#section name]]?  Plus an edit summary as you suggest.  That seems easy enough (WP:REDIRECT is not entirely clear to me on all this), so I'll give it a go and see if I get yelled at. 

 ::But before I start creating redirects, I wonder if the mouthful title List of residences of Presidents of the United States should be renamed first, as it is really more than just a simple list - though I suppose some some condensing and regrouping could be done.  What do you think?