S.L.
1) Like a PP, we have specific times set by the town we live in: 3pm-7pm. Parents with young kids usually go at the earliest times -- before it gets dark and colder. I plan on taking my kids out around 3:30pm.
2) Length of T or T depends upon how much candy you want in your house!! Do whatever feels right to you. Give your kids a nice experience but head for home at the first signs of fatigue. You don't need a major melt-down on the T or T route. Also, if you are in a busy neighborhood with lots of kids, this may not be the best time to introduce yourself to neighbors -- save that for another time.
3) If you teach your children to actually say "Trick or Treat" and "thank you" after receivng the candy, you will be very well respected! Tons of kids (especially the older ones without parents) simply walk up to the door and just open their bags, without saying a word. (I tend to give extra candy to the polite children!)
4) Lights on? Go ahead and approach the house!
5) We give out brand-name chocolates (not full size) and usually give two pieces per child. Toward the end of the night, I usually give more so I can get rid of it! However, I always give our immediate neighborhood kids at least 3-4 pieces.
The only other thing I can think of is that you may see Mommies collecting candy in a separate bag for her infant/baby in the stroller. I guess some Moms think taking candy for a child that cannot eat it is okay to do. Your children are old enough to eat candy, so this doesn't pertain to you. Just don't be shocked when one shows up at your door!
Have a terrific time with your kids!! :)