I don't know why, but for some reason when we go to Disney I LOVE having matching t-shirts. We don't wear matching shirts anywhere else, but at Disney we have matching shirts for everyday we are there. The kids roll their eyes and grumble under their breath, but they know that Disney means matching, and don't even try to get out of it! I think they secretly like it and that's why they don't complain more. Here's us last year in front of the castle in one of our shirts.
Check out the family to the right in the background they have matching shirts too! I just love the pictures when we all match. We even made Mickey tye die shirts. (I'll have a post on how to make them soon!)
For our iron on shirts I always get the awesome disigners (yes it's spelled that way!) on the DIS Boards to design them for me. Go to disboards.com, and there is a forum called creative disigns. There are disigners on their who personalize shirts for people in their spare time. The best part is, it's free! After getting the designs I print them on iron on paper and then iron them on. I always use the Avery brand transfers. You can get them at Wal-mart, Office Depot, or Staples. I have found they stick on the best and last the longest.
I usually make the shirts a tad big for the kids so we can wear them a couple years. We don't wear them at home, just at Disney so they will last longer. The ones we have now we have worn for our past 2 trips, so we decided to make a few new ones this year, and we will still wear some of the old ones. These are the new ones I made for this year!
Another advantage of having matching shirts is they make it easier to find your kids. We were at the Honey I Shrunk the Kids playground one time and I was trying to find Junior. I asked a cast member "Have you seen...?" and he automatically pointed and said "over there!" I didn't even have to describe him or anything. This could be really helpful if you have small kids who wander or can't talk yet!
Some people thing matching shirts are geeky. I think they are adorable. And as long as I can make the kids wear them, we will be one of those matching families at Disney!