I get the intention behind the analogy, but I know from experience that nobody ever comes away from it understanding what they're meant to. I don't think I've ever mentioned to a friend without them pointing out that balloons do have centers, or asking what's outside of the balloon. I've had much better luck just telling people why what they think is happening can't possibly be right, so they stop defending it or trying to reconcile it with reality, and then building up.
But, I'm not a physics professor. Your mileage may vary.
Ah, you do get it, I apologize for suggesting otherwise. Statistically, my odds were good, because you're right, and virtually nobody does it right. (I claim a Bayesian defense!)
Unfortunately, I don't know how to do any better. There's a leap to even abstractly understanding 4+ dimensions and a lot of people simply won't make it. Without that you've "already lost" regardless of how clever your metaphor is.
But, I'm not a physics professor. Your mileage may vary.