You must be so excited about your upcoming trip!
It is my understanding that when you start the ordering process online and put in the dates that you will be there, that your tickets are good for 7 days prior to the arrival date you input and 7 days after the end date you entered.
I don't have experience with the tickets because I will be picking mine up in 4 days-but from what I heard they are the made of Tyvek (so not the plastic KTTW ones, but like the normal one you would buy individually from Disney)
Also, you cannot have more adults than children when ordering....I would think that you should be able to have the three adults names and the three childrens names when you put the order in. But you cant make any changed afterwards. If you have an issue with that (which I doubt) then I would suggest just putting two orders in.
Jen