I'm going to say rude.
First, we don't know what they may have done in previous years and previous neighborhoods. Maybe they gave full-sized candy bars; maybe they did the same thing and just gathered candy from other people instead of buying any. So, we can't use the past as a guide.
Second, there was no need for the whole family to go. Yes, it is a way to meet the neighbors, but only the neighbor who is standing at the door, and only if the next batch of little goblins isn't coming up the sidewalk.
Third, it sets a bad precedent. If too many people are out gathering candy, and fewer people are at home giving it out, then those few are going to get fed up with feeding everyone else. Granted, I'm not that objective in this matter because of the declining number of participating houses in my neighborhood. Many of those dark houses don't have young children, and yes, I understand that some people need to work, or come from other cultures, or simply don't want to be bothered, but it was depressing to stand on the corner, and realize that I was the only lit-up house in sight. (My nearest neighbors are all on the "Don't want to bother." side.)