Yes, it's corny, but it was a lot of fun. My DD7 can pull an amazing vanishing act, and having those matching shirts made it a LOT easier to keep track of her. Something else I didn't realize until my son mentioned it -- not only do matching shirts make it easier for the adults to keep track of the kids, the kids have an easier time finding the adults. That was truly invaluable with the crowds in June.
FWIW, we did matching tiedye shirts, then personalized them with Disney iron-ons. I highly recommend
www.tiedyeusa.com for the shirts. You have to order 24 shirts to get the wholesale prices, but that wasn't as hard as it sounds. There were 5 people in my group for 4 days (20 shirts), and then we wanted an extra day of shirts for just immediate family (4 shirts), and then a friend ordered some for her family as well. The price averaged out to $5.25/shirt even with shipping costs. I'm not a huge fan of tiedye, but it was highly visible in the parks.
Good luck with whatever you decide.