Kinds soak up knowledge without having to ram it down their throats. Make it availablePerhaps I'm cynical -- but I see as one of the negative aspects of this fallen and sinful world: that a lot of the time people are, often strongly, learning- and knowledge-resistant. From time immemorial, those in the education business have had to battle with this tendency of the young -- who would so often rather be engaging in their own pastimes which they enjoy; than having to swot up dreary stuff in which they perceive neither point nor interest. (I don't mean to sound condescending or superior here: I was myself, like that at school.) Admittedly, to some extent, as per @Ken H above, kids can be curious and moved to ask questions about things -- but often that doesn't happen, or goes awry. My brother was a teacher for some years: his experiences in that occupation, caused him to conclude that supposedly educational school trips to museum-type venues (including preserved railways?) are a waste of time and everything else -- overwhelmingly, the kids just latch on to all possible inconsequential "fun" aspects of the outing; overall, very little solid information gets into their heads -- that is the last thing that they're interested in.
This pessimistic view is of course not an "absolute": some knowledge gets assimilated, however randomly; some individual kids do find such stuff interesting, and learn a good deal -- even about subjects for which they are not already enthusiasts. I cannot but feel in the main, though; that someone in @70014IronDuke's newly invented position of KASO, would need to be a magician (literally -- Hogwarts style) to clock up much successful achievement vis-a-vis his role. The same, I feel, goes for all "normals / punters" (child, or adult) visiting preserved railways -- very many of them will just want to enjoy the experience, hoping to find it relaxing / aesthetically pleasing (plus of course nice cafes, toilets, etc.): they won't want to be plagued with pesky facts, hitherto unknown to them and of no interest to them, about trains and railways -- and at varying levels of awareness, they'll resist such. (To be truthful, I can feel some sympathy for them here.)
Some learning on the part of non-railfans, will happen -- but in the nature of things I feel, not a lot. Even strenuous attempts to educate, will probably reap only a meagre harvest: prompting the question of whether -- with preservation societies' resources apt to be, in general, not very thickly spread -- it's worth investing all that much, in the learning-and-info side of the business. Have informational signs posted up, of course: they'll be mostly ignored, but some visitors will take varying degrees of interest in their content. Doing much more would, I fear, be rather throwing good money after bad.
Not a railway but the cafe at Wellesbourne airfield has aero charts embedded in the table tops. My kids/grandkids would look at those and then ask questions. Thats how you do it....