There's no need for a wagon/Avant when you get kids. The standard Impreza boot can accomodate most dizes of pram and all accessories quite easily.
Agter 6 months when they are big enough to go into a stroller, you can eaisly get everything in the back seat. I got my first Impreza for the precise reason it had 4 doors, a big boot and lots of safety features (ABS, side impact bars, airbags, 4WD etc). It really is a good sensible family car and we managed just fine with ours (mostly without rear folding seats!) and our boys are now 9 and 11.
Lots of new families get suckered into the "must have a people carrier" because they see all the other mums driving them. Most of them have smallish boots unless you fold the back seats down, have a high centre of gravity which makes the kids travel sick when the roll so much, and extra seats that you will maybe use one or two days a year when you travel as a family with grandma and grandpa at the same time. For the cost of lugging the extra seats, and lack of driving involvement all year round, just hire a big volvo estate for those two days/two weeks of the year when you need the space.
We even managed to go on holiday a few times, with all the stuff needed for a toddler and a baby in my car, and even our dog. It's amazing how much you can actually fit in if you are creative - remember that their feet won't touch the floor for at least 6 - 7 years so there's all the space behind the front seats that can be used as well - you can even fit a stroller in there after you get them seated
Remember that the wagons are slightly noisier than saloons, as you get more road noise coming through from the rear.
Having said all this, the newer cars are slightly better in some respects with the ISOfix fittings, more airbags and in the Spec D, better sound proofing and leather seats that wipe clean easily The 2.5 engine doesn't need to be revved so hard either and can be driven mostly everywhere keeping the revs below 3,000rpm for smooth and quiet progress and reasonable fuel economy.
Give me a shout if you want to have a look/test drive of a newer 2.5 car.
John