I played through the roiginal first and did HoW after that, but it was just bechause I finished the original before HoW came out. I think HoW is a bit hard for a too low level party, but also seem to remember that the game does a levelcheck. Anyway I prefere doing one part at a time so therefore first the original, then HoW.
IWD2 is a game much like the first. The story is nothing revolutionary, but if you are not fed up with the original after HoW then you'll probably like IWD2 as well.
And a tip for handeling the wife-unit:
I play IWD2 over the network at home with my wife. No complaints about playing too much when we play together and control half the party each (And she wasn't much of a gamer at all before we started.)