It's all about risk-reward.
Personally, my daughter is too young but I'm coming around to the idea that an occasional trip may be acceptable but regular trips are too dangerous for cumulative risk. Look around on this and any other motorcycle forum. They ALL have memorial threads for experienced riders who have been killed on their bikes. You can minimise your risk and ride safe but biking is still a high-risk pasttime. I'm also concerned about both me and my wife being on the same bike at the same time; I do not go out of my way to suggest lots of 2-up trips although there are limited numbers of shorter trips. Limiting the time of loved ones on the bike is my way of limiting the risk.
I'd be quite happy if my daughter decided she never wanted to own a motorbike.