My husband and I have good sons. We will leave them an inheritance. By the give it away logic, she shpuld also not pay for one bit of help after they turn 18. My step dad bragged that he never helped his kids after they turned 18. He is one mean bastard.
The small inheritance I received two years ago was a beautiful gift. It is allowing me to help a niece get started in college and get away from a bad family life. Niece has always been good and worked hard, but she needs help. It is helping us live a better life too.
It sounds like you are managing things very well.