It's funny. I was just reading an old post I made several years ago about almost the same situation. My dad even said the exact same thing to me about "it's not real trek, they are on a station".
Here is a link to the thread: Best episodes for a new viewer?
I hope they enjoy some DS9 soon. It is a great series, the best IMO.
That's a great list of episodes. I'm definitely going to make them watch "The Visitor" and "Duet". I think those episodes really emphasize what makes DS9 great, without giving away too many plot points. My parents hate spoilers.
I'd like them to watch "In the Pale Moonlight", but it's such a pivotal episode in the series, I want it to be a surprise to them. I predict that if they get that far, their reactions will be priceless.