We do a school wide move up day on one of the last days of school. It is similar to what you described, except we follow a complete school period schedule (47 minute classes). It is great for the incoming seventh graders, who get the true experience of switching classes, meeting teachers, having lunch, etc. on a regular schedule. I don't teach seventh grade, and actually would prefer shorter classes that day, but again, the day is really meant for them to get a real life practice at middle school, so it works and the rest of us just suck it up:) A few days before school starts, there is also a seventh grade orientation picnic for students and parents. Again, students get to check out their classrooms, and do a tour of the school, and parents get to meet all of the teachers.
When we have open house, we run a short schedule (about 8 minutes/class) like what you described. That also seems to work pretty well.
Anita, Our school does a similar orientation day just for 7th grade students before the MS actually starts. It is a half day where we get to meet the students, they go through a condensed version of the day and get to settle in before the 'official' beginning of school. I do like your school's orientation picnic idea though. How does that work? Sounds like a great way to start year.