I've only been to one party so far myself, but this answer sums up what I think as well.
Whatever a non-ticket-holder is doing up until 7 PM should be fine. Dinner reservations at 6:55? Go for it. Got in line for a ride at 6:45 and still waiting at 7? Of course you should be able to keep waiting -- I mean, heck, I'm sure you would rather have not HAD to wait in a line at all, so it's not your fault!
But -- not to be a jerk about it or anything -- but no, of course you shouldn't plan activities that start after 7 PM. And shopping, strolling around, eating QS, those are activities. It's not just about the parade and the fireworks. We went to the party to enjoy the whole park during that time. At the
MNSSHP I was at last year, those are things I liked doing during the party -- checking out merchandise in a less crowded store, strolling less crowded areas, and so on -- and that's why I paid for a ticket. If you didn't you're just crashing a "private" party, at that point. And that's all TOTALLY different from starting an activity before 7, and being allowed to finish it.