We suggest you run searches for your possible dates to understand the price ranges. For each set of possible dates, you can save a draft trip. There is no limit to the number of draft trips you can create, and drafts are saved for 48 hours before they are deleted.
Don’t wait too long to finalize your plans and book them. Keep in mind that prices and availability for airlines, hotels, trains, and rental cars cannot be guaranteed. Until your ticket is issued for trains and flights, it's possible things could change.