I have 5 sets of t-shirts and one set of hooded, zip sweatshirts that I had made just for Disney and other crowded, busy places. I got the brightest neon and tie-died shirts I could find. It took some looking to find the same bright, distinctive color in sizes from youth XS to Adult XL. I had them printed with a simple geometric design, (three stars), in a bright, contrasting color on both the front and the back. I bought extra sizes up in the youth sizes so that my 3 boys had shirts to grow into.
The shirts stand out in a crowd. They help us stay together. I can spot one of those shirts all the way across Tomorrowland. I have 3 young boys, and it helps me keep them in sight when they are walking around. When I am hysterically looking around for one of my little wanderers, it is amazing how many blond-haired little boys there are that look like mine. If I can't see one of them and I call for them, people around me know who I am looking for and point him or them out.
We wear a different set every day. I find them very helpful.