We usually make t-shirts for our Disney trip. Usually wear them one day for a special photo.
On our recent trip with 17 family members from 4 states we decided to simplify our pre-trip work and not do shirts.
We did pick a different color for each day - teal for MK, green for Animal Kingdom, etc. Then, each person/family group could buy their own shirts or use one they already had. This provided great looking group photos.
And a couple months later, we know where we were each day because of the shirt colors. Easier to make memory books.