I have happy memories of flipping through (Britannica and World Book) encyclopedias as a child, but I also agree with the perspectives in this Slate article
My advice is to make the wiser, cheaper choice, one that will prove more helpful to your kids in the long run: Pay nothing to Britannica and teach your young ones to use Google and Wikipedia. While there are many legitimate complaints to be leveled at Wikipedia (rarely, it gets things wrong; sometimes, its entries are vandalized), the free, crowdsourced encyclopedia is better than Britannica in every way. It’s cheaper, it’s bigger, it’s more accessible, it’s more inclusive of differing viewpoints and subjects beyond traditional academic scholarship, its entries tend to include more references, and it is more up to date.
Most importantly, learning to navigate Google and Wikipedia prepares you for the real world, while learning to use Britannica teaches you nothing beyond whatever subject you’re investigating at the moment.