Ouch! I ruined a visit to the beach as well one day, I think I was 10 also, not long after we had moved. We were at a beach, I had found a sea urchin's casing, and decided to scare my brother by skipping it in a puddle next to him. Reared back and spun it -- and it hit him square in the side of the foot! A couple spines went in, and we had to go to the hospital. Doh! :)
My wife @countrylover is also a Leo (as is my mother!). I'm surrounded by roaring lions! :D
I have 2 boys. I can imagine your scenario all to well!!!