There are no timeshares in Chatham. The closest are 10-15 miles away. Since I would consider July to be the reddest of the red months, it would be difficult to exchange into one now.
Here is the search I did on Google – chatham mass (Motel,hotel,inn,b&b) and got numerous hits. I’ve never stayed in Chatham (or nearby) so I can’t recommend a motel/hotel/inn/b&b but they all looked nice when I either walked or drove by. Some do have views of the Atlantic Ocean; those would be on or just off Shore Road.
Maybe you could rent a house for the week you need.
Since July is the busiest month on the cape, I would not delay in making reservations now.
SBtS