Kyoto Station is basically a massive shopping mall that happens to have trains running through it - and this is pretty typical of Japan's major stations. But here's the really important bit: this is where you'll want to grab your ICOCA cards (think Japanese transit cards), and there's a crucial tip about this that can save you some headache.
Bring your kids' passports! You'll need them to get the discounted children's cards. These cards are pretty cute - they make chirping sounds when your kids use them on trains and subways. It's actually a clever system since kids ride at a discount rate. Pro tip: keep track of whose card is whose since adult cards are charged full fare.
While you're sorting cards, take time to explore the station itself - we're talking 15 floors of shops, restaurants, and even a garden with city views. The architecture is wild (thanks to Hiroshi Hara), making it worth a visit even if you're not catching a train.