I always think mid-afternoon events are difficult to figure out how to feed people.
If I'm planning to serve a pretty heavy spread at a time that is not a traditional meal time, I usually inform guests when they RSVP that there will be a buffet lunch. I don't think there is anything wrong with serving a full lunch mid-afternoon, especially weekends when many people will have a late breakfast and be ready for another meal around 2 or 3.
I agree--they cna be hard to figure out!
In my ILs' family, they would expect a full meal, even at 2. Whenever we have a restaurant gathering for someone's 60th b'day, etc., it's a meal, and it's at 2pm. (part of that may be that the restaurant will only block off the space at 2, or something, but still...)
In my parents' circles, 2pm would probably indicate desserts and hors d'oeuvres. But still there's be enough that several people could probably make a meal of it.
Geography may have a small effect--I find that all meals are later here on the east coast (or in NYC) than they are for my friends and relatives in the Midwest. Here, most people each lunch around 1pm, and 2pm is not considered a late lunch (12 is actually considered a little bit early); my impression is that most of the people *I* know in the midwest are definitely done w/ lunch by 1.
Dinner is also later here--it's completely common for people to eat supper at 7pm, it's about 6 for the folks I'm acquainted with in the center of the country.