While I don't mind talking technical things over lunch, I firmly believe that (en)forcing work-related things over lunch is a bad thing. I think that lunch should be a break from work and hence work-related stuff should only be brought up if it's really important (to you, obviously). You cannot expect the others to care (obviously) and I see the "never seems to go anywhere" underlining that.
If the issue is important to work, people will set aside time outside of lunch for it. You could try to arrange a workshop before lunchtime and then go to lunch together after the workshop to discuss the stuff (making the lunch some perk, like bringing in outside "special" food or even going outside might be something to keep the people together). But I'd try to avoid forcing the mixture of private/personal stuff and work stuff - it will only end in people rejecting the goal (Perl) for the wrong reason (they want to eat when/where they want and talk about what they want).