It's also possible that it will cost you the same as if you'd just bought them from WDW. To use your situation...... You buy tickets from the broker. When you go to upgrade, WDW will credit you for the amount the broker paid WDW for the tickets - not for the amount you paid the broker. The amount the ticket was sold for is encoded on the ticket. I'm not 100% on the details, but it is at least possible that you would be better off with a (reputable) ticket broker who can sell you a 7-day ticket with the extra options already on there.