I think you have to be 4 years old, not 3. My younger DS had recently turned 4 when he did this a few years ago and if it wasn't for the fact that his older brother was doing it, I don't think he would've done it in a million years.
That sucks that the fireworks were cancelled last night. I remember a few years ago coming out of Le Cellier at Epcot and there was a horrible thunderstorm and it was insanely windy. Well, we finally decided to just go for it and walk back to the Beach Club and to our shock, Illuminations was going on. So, it probably takes a lot for them to cancel the night time shows if they're weather related.