Hiya David! Welcome to planDisney! Greetings from across the Atlantic!
Oh boy! Spending three weeks at the
Most Magical Place on Earth sounds like a dream come true! Just think of all the wonderful experiences that await and the magical Disney memories you are bound to make over that time! Not to mention, being able to purchase 14-day park tickets is one of the major perks awarded to Guests from the UK!
In regards to your question, you do have an allotted amount of days to use your tickets within. It seems like the
14-day Magic Tickets give you an 18-day window that will end on August 22nd if you start using them on August 5th. Unfortunately, this time frame cannot be extended, since tickets are priced accordingly for the number of days. It may be possible to delay the start date of your tickets if you don't plan on visiting the parks for the first day or so. You'll need to
call the Walt Disney World Resort and speak to a Cast Member. They will be happy to assist you in any way possible.
If you want to add on a day or two toward the end of your stay, you can do so when you arrive onsite for your holiday. You can visit the
Disney Ticket Center at Disney Springs or any ticket window outside of the four theme parks. You can also do so by visiting the US-based Walt Disney World website and purchasing tickets online. If you decide to do this, make sure to book your park reservations for the parks you want to visit on these days. Park reservations along with valid park tickets are required for entry each day.
David, although this is not the news you were hoping to hear, you will have plenty of options to visit the parks throughout your entire length of stay. If you were planning some additional activities throughout your trip, it might make sense to plan them for the last few days of your stay. Regardless, you are going to have an amazing time!
Happy planning!
Greg