the kids were the same age as in his vision, yet it was 2(?) years later, so they'd have been older
I think in real life the top didn't spin at all. The whole point of the top was that in another person's dream, it'd behave without the odd weighting – ie like a normal top (that's the whole point, so you can see if you're in a dream or not). when he span it in real life, it never started spinning, due to being weighted. I think the point was, as it was spinning at all, it was in a dream. He said something about 'it'll spin forever if I'm in somone elses dream' but that doesn't make sense, as in their dream, the top would have normal physics (spin for a min then drop).
Other possibility is that, if the location was architected by the young girl, she knew how the top behaved, so might have made it that way in a dream
good film though, kinda matrixy in ways