My 9-year old does the same thing. Normal bladder control, etc. Sometimes she forgets to go to the bathroom and if she laughs hard she'll wet her pants.
One day she was at gymnastics and she was laughing and she wet herself. Because she was in a leotard and sitting on the mat, everyone saw. We had to get a custodian to clean up the mat and since I was working she had to wait on the sidelines in a wet leotard. She was very embarrassed.
Since then she ALWAYS goes to the bathroom before gymnastics (without me having to remind her) and she's more careful about remembering to go. I felt so bad for her that she was embarrassed at gymnastics class, but sometimes it takes those hard lessons for a change to happen!
She'll live through the embarrassment. Sometimes life has to do the teaching when they won't listen to Mom and Dad!