We recommend booking immediately as summer is extremely busy on the Cape. The main hotel is The Dan'l Webster Inn & Spa. To book, call them directly at 800-444-3566 and say you're with the Tremulis/Ritchey wedding for a discounted rate. There is a two night minimum. If the hotel doesn't have what you are looking for - there are a few other bed & breakfasts right in town just a short walk away.
If you would like to rent a house, Airbnb and Vrbo are operational on the Cape. WeNeedAVacation is also a very local website with additional rental properties.
Other options include a 20-30 minute drive to Falmouth or Hyannis with plenty of hotel options!