LEGO is great and pretty timeless. I would keep all the sets and then let the grandkids play with them, plus they have all the cool tie-ins with IP like Starwars etc, that's always going to be good.

as for inflation pricing feeling lower, i think it's probably because the calculators use official cpi and other indicators that are a bit of a scam, that and certain things will have regional price fluctuations. we all know inflation is always way worse than the offical numbers