MY compliments, you've managed to tie it off quite nicely despite loosing interest in it. I would suspect that Harry's children are magical by virtue of his different "polarity" and it's unlikely there'll be any others for a good while, if at all. I can see the Potter's becoming a presence but not a power and not expanding their family to where another wizarding age is possible. I do like that the two couples stay in contact, as infrequent as their lives may make it, and 'twill be good if their children do likewise. I quite liked the quote from a history text with which you started this chapter; it settle a lot without being too dry or too sleep-inducing" (some folks do info-dumps that are as dry as Binns' teaching). Speaking as someone who works with technology, I wonder how the world will recover technically and what different paths, if any, they'll take this time? If nothing else, the reduced stock of petroleum should lead to an emphasis on photochemistry with the goal of artificial photosynthesis to create fuel and lubricant stocks will leaving the remaining petroleum for feedstock use. It'd be interesting if any nuclear-powered vessels survived to help renew civilization. Lots of material to think on, here.
Bravo!! for a good and enjoyable story.