@Bonnie81 For those periods of time that are highly desireable you can change the nightly rate up to reflect a higher demand. If that is July for you, then go to your calendar and increase the rate.
Hosts can opt to provide a percentage discount for a weekly booking but you don't have to. If you do, Air BNB will take the deduction at the time of the booking. If you are concerned about cancellation you would need to adjust your cancellation policy before any bookings.
As for payment, Air BNB collects the full amount owed at the time of the booking with two exceptions: Long term multiple months booking payment and split payment. Neither of these situations seem to apply in this case. Look up in the Help Center about these exceptions if you are curious.
So, the other issue for you is that it is a neighbor and you probably have a personal relationship to manage as well as a business relationship. That is always a problem to balance. I think you should be open with the neighbor about the income potential for you and your desire to be helpful to them.
Good luck!!