My 12 year old is using rotary cutters in her sewing class at school. But she goes to that class every day and had to have a whole class on safety before using them. All the rulers also have finger guards on them. I don't worry about it. But the teacher has been teaching for years.
If it were me for a shorter period of time than DD's class I'd go with precuts for peace of mind. But one on one I think kids that age are fine with rotary cutters so long as safety precautions are taken. I remember using them around that age as well.