Free-Range Parenting Question: Is it okay to offer to help?

So, I am a big reader of the Free Range parenting blog (and articles, and books, and all that goes with it). I was reading about the parenting in different countries, during vacations in Thailand, and here.

And I had a question, so I'm really hoping that any free range parent can answer this for me, from their perspective.

Last month I was traveling, in the U.S. - my husband and I took trains and planes, and it seemed wherever we'd go there'd be kids and parents. Anyway, I'm wondering, are we too overprotective in this country to accept help from a stranger, or should it even be offered? I'm thinking not of anything specific, but I'll try to give an example.

I'm on an airplane (or in a restaurant, or public place, etc.) and I see a parent having trouble: their toddler needs to go to the bathroom, they're the only ones in the little group, and they have an infant. Is it acceptable to offer to watch/hold the infant while they take the toddler in the bathroom, or is that now a major danger alert for parents?

I refrain from doing anything like this, on the off chance I'd get a violent reaction from the parent thinking I'm a kidnapper or something - but I really feel bad in situations like these, because society is so much safer when people help each other.

So should I offer and take the consequences, which might be as little as a polite refusal or even a grateful, "that would be wonderful" or might be as bad as someone being paranoid and reporting me to the police or other official (I don't know for what, exactly, possible harm?)

I'd be interested in answers: is it okay to offer to help?