1.Wait until you are at least 2 days past the 11 month window for a 9 day stay or 3 days past the 11 month window for a 10 days stay and book it all at once.
2. At 11 months exactly book 7 days then call to modify the reservation and extend the stay (must wait at least 2 days for 9 day stay or 3 for 10 day stay but call before the 7 days are out)
1) We are very date flexible.
2) Number 1 is moderated by when it starts/stops snowing. We will not fly in snow. Too many Airline surprises.
So, we go in Mid April, Early November. For US - these end up being optimum for lower crowds, lower point costs. Everyone is different: we don't have to worry about School Schedules, or work vacation Schedules. We DO have to worry about Airline Performance.
Since you are booking during a busy time, I would book online on the first day available and book your 7 nights. Then call the next day and add a day, then do it again each morning until you get your desired dates. I do this every year as we go 14+ nights every May and October.