If you're weighing the difference between you driving the HCH and your wife, then it might help to know that fewer long trips will get you better gas mileage than several short ones. 12 miles one way isn't VERY long, but in terms of who would do better with the hybrid, it would probably be you, not your wife.
Lots of short trips to get groceries, run errands, pick up the kids, means that the engine has to warm up every time, that there's a lot more stop and go, start and stop, sitting just long enough to cool down and then being restarted again... not the best way to maximize a hybrid's fuel economy. Still, if your wife is putting substantially more miles on a car than you, or if she has to take the kids to lessons that are really far away on a regular basis or something that approximates a commute, then it's possible she could end up as the more efficient hybrid driver in the family.
As for the bigger question- is it worth it?- I think the answer is most definitely yes. It's true that without knowing your alternate purchase, it's not possible to calculate your exact gas savings, but it doesn't take a math genius to know that 48 or 50 miles to the gallon (which is completely achievable with a little effort- see the database) or even just 45ish (with no effort to speak of) is about twice the fleet average. The HCH is a great car, fun and easy to drive. It's socially responsible, it's got a great safety record, and it's energy efficient. If you drive it long enough, studies have shown that it probably WILL save you money.
Plus- there's the 'fun' factor of hybrids. If you do let your soon-to-be-driving son take it out for a spin someday (far) down the road, he and all his friends will just love it. You could be the cool dad with the hybrid!
