Jaspen, before we decided to put it off for a few years we did a bit of research and we decided that we would prefer Hakuba because while it has some English langauge instruction for the children and so on it's a more Japanese style resort than Niseko. It's got snow monkeys which sealed the deal for me.
I spoke to a package company and they were really helpful with recomendations. For the children in Hakuba you can get instruction in English from Evergreen (just google Evergreen Hakuba) or they also recomended a baby sitting service called
Hakuba Mommy. If you google Hakuba babysitting it is the first result.
The guys on my ski forum all recomended getting a package for the first time because usually it works out to be the same price as doing it all yourself witha whole heap less stress. The package companies will arrange hotels outside the skiiing areas too if you want to do a bit of sightseeing.

HTH.

Pucci, thanks for you advice. Our current plan is to put it off until both the boys are a little confident on skis and Imran doesn't need creche or baby sitting. So I'll come back to it then.