I never saw anyone with their families at the orientation
Where did you hear that you could bring them?
Is there any way that your family could follow you to Japan a week or two after.
I know there is a strong desire to bring your family with you the day you get there, and many people probably have done it and loved it, but looking back at my experience I'm glad I didn't.
My husband came 2 weeks later. That was more than enough time for me to get adjusted to some crucial things without worrying about him baking to death in our un air-conditioned apartment, with no internet, no stove and no car. We literally had almost nothing when I got here and it was important that I could focus on my work place, and acclimatizing myself to our town a bit before he arrived. It actually helped me figure things out (like where is the grocery store, and what do I cook, and also getting some well needed sleep and rest after Tokyo Orientation).
That said, if you have kids, being away from them for too long can be a challenge in itself. If you can bare it, and they can bare the solo journey with their other parent (maybe with the assistance of a friend of the family to help with the flights, luggage, child wrangling, etc.) a week on your own would be in your favor.
I would also like to say, you might have a crash and burn experience right around the time you get to your town.
It's the exhaustion, the orientation, the jet lag, the culture shock...maybe you'll be fine...but if you are anything like me, you will find yourself about to break down in tears while watching the Japanese shopping channel on that first in my apartment. Having a mini meltdown on my own is always much better than my whole family having one along with me.