Bright colored T-shirt. On the back of all of them, print (arranged nicely--maybe around a stylized "mouse" or something):
VERA
1952--2002
Celebrating 50 Years
at
Walt Disney World
Or, maybe this one:
Venturing through the World
for
Vera's 50th"
Then, on the front left breast area, put "I'm Vera" on hers and "I'm with Vera" on the rest.