I also would want the rear two seats only for luggage/occasional use, something about them being that close to the rear screen makes me shudder.
With them up, you have virtually zero boot - room for a couple of carrier bags. But the Zafira does have them permanently fitted in the car, unlike some of the others where you have to clog up your garage/shed when not in use.
And, in the Zaf-A, they are surprisingly comfortable - I sat in one for the first time on hols when Mrs TB drove back from pub, normally it ends up being either mum or Mrs TB in the boot. For me, the middle row of seats had to be slightly forward, which the Zafira allows.
Going by MDTM's posh (Elite) Zaf-B, they are a bigger car than my supposedly posh (Elegance) Zaf-A. Not sure on size difference between Tourer and Zaf-B (certainly, tourer is bigger than my Zaf-A). MDTM's Zaf-B is a damn site more comfortable as well.
However, if you need to cart other peoples little baskets with you, I think you possibly need to except one of 2 options:
1) Learn how to say opps off to them, and get a car that suits
your MrsT's needs/budget/capability
or
2) Get a far bigger MPV, such as Galaxy (and clones)/Espace/other crap French shite, and accept the hit on budget and running costs.
As for auto, esp around town, maybe persuade MrsT to take a proper test? It'll likely be useful in the future anyway, even if you still end up with an auto?