If the power went out and the water didn't hit the gear while the power was on chances are VERY good that it can come back to life with a washing in distilled water and a chance to dry.
I don't know how the guitars were stored, but if you dry them properly chances are very good they will be OK.
The key here is not to panic [!!], assess the damage and go through a methodical cleanup.
If you have home-owners or renters insurance that should cover the water damage to the physical space [floors, etc.]... and as the water was only 6 inches deep [I know it seems like a lot, but its not] you're probably going to come out of this in not quite as bad shape as you're imagining at the moment.
Just breathe, and while you will have sustained some loss, its not going to be a total loss. While I know it seems bleak at the moment, try to keep a positive attitude, work through each item next week, and be thankful that your kids are OK and that it was only "stuff" that might have been lost [I had a very dear friend die in Katrina... and not to minimize your plight, the fact of the matter is that you and your family are and will be OK].
Feel free to PM if you think I might be able to help you with any advice on how to figure out your losses and/or get yourself up and running again.
There was a similar [less damage] thread running -
Rack Gear + Water = ? I posted some "cleaning" suggestions that might help in your situation.
Peace.