You will not receive cash back toward the tickets you have - there is no GAD gift card option (like there was for the birthday promotion last year). You are maxed out for MYW tickets - they only go up to ten days. Like the PP said, you can redeem the vouchers for the pin set. A few other options:
Even if you are going at a quiet time, the FP exchange cards are awesome, particularly if you are a Toy Story Mania fan. We rode TSM three times with the FP cards and used our park tickets for ToT and RnR FPs. This was in July, and FPs for TSM ran out at 11:15.
Since you are staying for two weeks, you can redeem your GAD vouchers for admission if you plan to spend more than ten days in the parks (since you can't add days to your 10-day tickets in your package). You can also upgrade the GAD tickets if you want to spend more than 11 days in the parks.
You can save your ten day tickets for another trip and upgrade your GAD vouchers to ten-day tickets for this trip. This requires a pretty big financial outlay now, but it might save you money in the long run if you plan to be back to WDW in the future. Unused package tickets never expire. You could also downgrade the tickets in your current package to one day (or two-day if you have free dining), save those tickets, and upgrade your GAD tickets. Since you are within 45 days of check-in, Disney would probably charge you a $50 change fee, so that might not be the most economical option.
Edited to add: I was too slow - Doconeill covered everything in his post.
