When my children were younger we used to travel with several other families. One time a friend and I took our then five children to Sea World of Ohio on a summer day when the place was packed. We dressed each child in striped polo shirts and matching shorts, each in a different color. They were easy to spot, and we got a lot of comments on how people could tell we were together.
Later, we took eight children and three moms on a variety of day trips to crowded places. We all wore the same Tee Shirts, (some we made specail, some we already had from VBS at our church), and it was, again, easy to keep track of everyone. As they got to be teens, they objected to this "dorky" way of traveling, but as the responsible parent, it made my life a lot easier! Now, of course, tee shirts are a wardrobe staple, and they all (young adults - youngest is 20!) think matching Tee Shirts for an event is great!
I love seeing family groups dressed similarly. It's being proud of being in your family or group! Enjoy it while you can. I am hoping for a family reunion in the next few years and we will definitely be wearing matching shirts!