Myself and my wife have been addicted to convertible cars, and could never have a car with a roof...

If you have a little guy or gal on the way then you may want to reconsider this. Consider that for the first 18months they will be unable to tell you that they have earache, or that the wind noise is bothering them, or that they are cold. Aside from screaming uncontrollably at you that is...
Figure that every time you take the little person in the car that you are going to have to put the roof up anyway. And that (unless you have a ready supply of nearby relatives to babysit a lot) you will be taking the little person in the car a lot.
Now work out whether a convertible car is really that necessary if you only actually get to put the roof down for 10% of your trips. Especially if having that convertible means having a non-optimal vehicle for your purposes.
I personally think that you be far better off with something like a small station wagon with a sunroof. At a push a hatchback would suffice, but this would leave luggage space tight. Probably ok for everyday usage, but you'd hit problems with vacation type trips (assuming you want to take the dog and child on vacation).

Maybe you should keep your old 'car' to satisfy your convertible cravings. I guess it depends on how much you think that you'd get for it, or what the insurance delta is going to be to keep it as a second car. I'm guessing that it's definately an option worth considering.