Let's get the space thing out of the way because it didn't look like it was going to fit us at all when I first saw it. But fit, we did. I'm 161cm so I will pretty much fit in most cars. My taller husband was also able to squeeze into the driver's seat, and while he couldn't put his seat back to his preferred position without the kids complaining, he did have enough head room.
My two children, aged 5 and 7 also fit in the back seat, much to their disappointment. They had taken one look at this car and wondered how they would fit in there, but they were able to without much trouble. Yes, their legs were closer to the seat in front of them, but behind me they were fine. It's when you're trying to sit behind a taller person that things get a bit squishy. The back seat is quite compact.
The boot however, really surprised me by having enough room to fit a pram in there. This is a particularly bulky pram that we test with and won't even fit in a Mazda CX-3, so for it to fit in a Picanto was amazing to say the least. At 255L it's one of the biggest in it's class, but most of the room comes from depth, so it's good for a pram or for suitcases, but groceries will have to go on top of one another.