We have a 2.5 year old and reguarly drive up to my mrs parents barn in Suffolk and have no problems trouble fitting all the baby stuff in the car. My wife does not pack lightly either ( as most women don't ). Yes an estate is more practical but if your only using the car weekends for kids and the rest of the time your car is a daily commuter then the Golf is a perfect match. I've driven various cars and the GTI is by far the best car I've ever had the pleasure of owning in all departments.
My dads got the new 3 series (the diesal sport one) which I driven fairly often and yes this is also a great car but not as fun a to drive as the GTI. Alot of peolple on here don't like the leather interior on the golfs (as their cheapskates

) but again I really like the look and quality of it and have had no problems with wear. I find the interior a bit dated on the 3 series but the build quality is superior and feels just that bit more solid imo.
and so to summarise.... its Golf GTI's for young Dad's and 3 Series BMW's for Grandads

Hope this helps and welcome
Martin