I’ve had a 2012 Mazda5 for about 6 months now. I love it. I really can’t think of any flaws in it, considering the price.
My requirements were: fun to drive, manual transmission, a wagon (but not Golf or Mazda3 size), and 3 rows was a strong plus. The only comparable cars are some Subarus and the VW Jetta Sportwagon, none of which have three rows or much better mileage. The TDI VW has excellent mileage, and I loved my 02 TDI - but fuel pump failures with the current engine scared me away.
It drives great. My previous car was an 04 Audi S4, and in many ways I prefer the Mazda5. It is much lighter on its feet – easy and quick to maneuver. The S4 was much more powerful, but slightly ponderous. The shifter is nice, I find the engine power to be just fine. The suspension is smoother than my Audi which had 80k miles on it, but still very planted. The interior is very ergonomical, and simple. And the size is exactly what I wanted, before I even knew I wanted it. We often transport my daughters’ friends – and it is no problem. But for normal use – we have a big hatch/trunk area.
To answer your question – you absolutely can not fit a stroller with six people. If you use the third row – the space in the back is minimal. It depends on your priorities – if you want the extra space – you basically need a bigger, less fun to drive and less fuel efficient minivan or SUV. If you have 3 kids – then more space is probably a requirement.
But in my case, and in my opinion, if say I’m taking 4 kids and a wagon / stroller to an amusement park – I will either strap the wagon on the roof, buy a hitch cargo carrier. That will happen only a few times a year, for the remaining 360+ days I’d rather drive something more fun.