Quite a few people use Sportwagon's as baby transports, as Wrinx said technically the boot is slighty smaller than a saloon, but being a hatch it's easier to load and you can stack it higher behind the nets.
12K would put you in a delivery mileage brand spanker if you haggle. Natural choice of Engines is probably the 2.0JTS Petrol if you are coming out of an MX5, but don't overlook the diesels, the 2.4-20V will out pull the petrol easily, with almost GTA matching mid range punch.
Come to think of it 12K would get you a good second hand 3.2 V6, GTA Sportwagon... very special
The 166's a great looking car, but beware of eye watering depreciation in our prejudiced market
Don't worry too much about the fabled Alfa reliabilty problems, apart from Spaghetti suspension bushes, (Make sure they change them at about 12K under the warrenty), they are no better and no worse than the majority of cars.
Good look with the car and the new arrival and welcome to AO.