I worked for many years with special needs young adults. We had a delightful boy who became brain damaged from falling off his bike and hitting his head.
I always insisted my sons wore a helmet. When my son went riding without a helmet I did not let him use the bike for a week. He never again went out without one.
Don’t chas vesholom come to a matzav when you feel guilty and say “If only I had insisted on the helmet!”