Also people steal things. Taking something that is very valuable and rare out of a highly secure area and putting it into a non-secure area is not very smart. No one has a problem with museums putting valuable and rare things behind glass or in secure areas, so why can't libraries do the same?
I know I'm a bit behind but I've not been here for several months because Real Life got fizzy, but...
When my children were small and we went to museums, and National Trust houses, and the like, we played something called MySister'sName's Game (because my sister invented it). The way it goes, you are permitted to 'steal' one thing from each gallery or room in the stately home. Hammer Space rules apply, so it doesn't need to be something that you could actually carry: it is assumed that anything up to the size of a small traction engine will go into your backpack. You do, however, have to justify your choice (this can involve accusations that 'your thing is stupid' etc etc cont page 94, but actually 'because I like it' is a justification). I have had to explain the rules of this to total strangers who have heard us playing, and then caught them playing themselves later, including one child aged about ten who came thundering back up a corridor, screeched to a halt in front of me, and asked breathlessly 'Are you the lady who knows about the stealing stuff game? My brother says I can't take the ceiling from the Great Hall because it will make the roof fall in, but I can, can't I?' (Yes, he could.)
It's a really good game to keep small children a bit interested and to make them look around rather than just trail disconsolately from room to room, sighing loudly, but a Very Important Thing To Remember: do not allow your child to walk into the room, stop next to the room guide/security person, and ask in their outdoor voice 'so what are we stealing from in here?'
Do not ask how I know this.
I love this game! I had to read it twice to be sure, but I do. We did something similar when I was a kid but more like "you get to pick one thing to keep" so not using the word steal....
Maybe "one thing to remember forever" would work as phrasing?
Or, "Putting it in my Evil Lair!" when I was a kid, we'd pretend to be super-villains and big/awesome things were on the list to put in our lairs when we got one.
On a side note, if the Indiana Jones Ark of the Covenant, van Gogh's Irises, da Vinci's Girl with Ermine and all the Gothic grotesques in the world disappear, do NOT look in my secret lair!