I wonder if people who feel this way (not saying you personally) must come from smaller towns? That don't have to deal with strangers all that often?
Every morning for work I ride the CTA. It's the EL-train here in Chicago, like the subway in New York. Everyday I am on with people from all walks of life and some interesting characters, shall we say. Sometimes I'm with very few people, sometimes I'm a sardine. There is no one (like a driver) on the car with us and trust, if I were to push the intercom emergency button, no one is coming!
There have definitely been times where I have been uncomfortable and there were a couple to a few times where I've actually been scared.
The difference with gondolas - you are in Disney World. You are not going to be on a gondola with some of the characters I encounter on my way to work. I can't, as a woman, imagine being nervous to ride with a group of strangers on a gondola heading from a hotel to Epcot.
Also, we travel as a couple. It never even occurred to me that a family would find it strange if we climbed in their gondola with them (if there was room for us).
Regardless, I doubt this will be an issue and I'm sure most people aren't going to bat an eye at riding with strangers.