Welcome Badget: It appears to me as if you have some diametrically opposed challenge's. "I have a wife and 2 kids and need to save some money somehow." I'm not very confident you can have a wife and 2 kids, as well as save money somehow. However, I think you'll find their are a number of people on this site who can empathize with your circumstance.
I acquired a 89 Honda Civic Wagon about a year ago, largely because I was getting very exasperated with having to visit the gas station. The Wagon was a fair choice, for me because when I need to take someone, or more than one someone, I can still do it and get fairly decent mileage.
One thing you can do, which will help a bit, is run your tires at a pressure higher than the max on the sidewall. When I boosted mine to 55 lbs I was really surprised at how much farther it would roll, compared to prior. It gives a little harsher ride, but I've been running them their for about 6 months and I haven't seen any other adverse issues, besides the ride.
Their are other things you can do, but if you can swing it, you should get something like a Honda VX, where you can get more like 45-50 mpg. Best of Luck