1. Gift Unused Credits to Other Guests You Meet
If you don't have the extra packing room to accommodate all those prepackaged goodies, or if that feels like too selfish a use of your left-over credits, you can use them to add a little magic to somebody else's day before you leave.
On your last day in the parks, look around and try to spot a family or group who you feel would be the perfect candidates for a bit of generosity. Once you've found the right group, approach them and politely ask if you can treat them to a snack or meal with any unused credits you have left. If they decline because they don't want to take away from your trip, simply explain that those credits are going to expire anyway so they might as well be used for something good.
You might be surprised what a gesture like this can do for somebody's day. If you're able and willing, give it a shot!