Not to throw a bucket of cold water on things, but I think eating together may add in a bit too much.
If you figure getting in line at 6:00 (may be a bit early, but let's pad it out for now), and an hour of goofing off in the parking lot (taking pics, etcetera; also maybe a bit more than necessary), then from 5:00 on, its all about the show.
If we do a joint dinner at a "sit-down" restarurant (like TGI Fridays), count on at least an hour, maybe an hour and a half. So you'd be talking sitting down to dinner at 3:30 - 4:00 to allow us to head out to the filming spots for pics at 5:00-ish, and the line by 6:00.
Now, of course, this all assumes a certain order of events, and some padded time frames. You could move things around, take a few pics in the film locations first then eat later (around 4:30 or 5:00) and that would allow enough time to get to the line by 6:00-ish.