Having kids sometimes come over while we work is pretty cool. They ask questions about what we're doing at times and we have to ELI5, it's great practice.
My desk has a number of puzzles and they have a ton of fun playing with it. Sometimes they draw on the whiteboard or write a quote.
A++, would definitely recommend bringing kids a couple of times a year.
I've found it really breaks the ice between colleagues .. especially when our kids make friends/make drama independently from the office politics - it somehow unites us. :)
Of course it helps to work in a company producing things that might be actually interesting to kids in the first place. If all you're doing web-blah, ymmv..
