Welcome, SF4!

Too bad you have the mandatory training. But Oct 8 is awfully late in the season, anyway. Snow often flies by then, making the trail more difficult.

There are plenty of unused / no-show permits this time of year, so you could go ASAP, and use those to hike. Here's the link for the Unused Whitney Permits - 2011

You can get the no-show overnight permits at 11 AM at the Visitor Center to start hiking the same day. If you are there at the 11 AM time when they declare the no-shows, and if there are a lot of people lining up, they hold a drawing to see who gets to the counter first. I fully expect that there would be plenty of permits to go around at that time. (Also, if you stop in about 8:30, as others are picking up their reserved permits, a few become available as they free up some slots because of people dropping out of their group. These can be requested as they become available.)

The unused numbers are what is left AFTER that 11 AM rush, and after anyone asking gets processed throughout the rest of the day. Of course the availability is even better if you are there Sunday through Thursday.

Finally, keep checking the online permit availability. Here's the link:  Mt. Whitney Trail Overnight Permits.  As I write this, there are currently 5 slots available for Sunday, Sept 16.  A few good people will actually release their reserved permits online, especially in the few days before their hike date. (If you see some you want, and if you call the Wilderness Permit number, 760-873-2483  they might be able to actually exchange the permits without your incurring another $15 per hiker charge. I'd call and ask about this though.)

I would definitely try to go this month! And good luck with the 6-year-old. That should be a real highlight for him.