lyn, fivez.. I love japan too but getting kinda overdosed. Ever since i met my hubby, we go there at least once a year. my in-laws go super often too.
i think hokkaido is better to drive around in summer. For winter wise, it is better to go with tours cos the snow is really heavy. i went there on package tour.. quite a quiet place but love the food/choc/snow. I also did the same as u.. stay at 1 place and travel out so that no need to move luggage.
roger, One of my fav boutique chains is hotel villa fontaine(hvf), but not so sure if it's good for travelling w babies. HVF osaka is located at shinsaibashi. Are u getting JR pass? It's good value if u are going to take shinkansen a lot.