$20-$30? They got off cheap. I told my 17 year old that is he is still home when he's 18, he's paying a third of the bills since there are 3 in the household.
First off, this might come across as brash..first cup of coffee. We do not receive a handbook on how to raise children when they are born. We all make mistakes. There is no right or wrong way. It's trial and error.
You taught them what to be afraid of...not how to embrace life and enjoy it. Sure we all want to keep our children safe, but life isn't about playing it safe all the time. Take the training wheels off already.
We have to take risks and learn to rely on our own intuition. Do your children know how to balance a checkbook, pay bills, clean? These are things we are to teach them too along with the awareness of danger and awareness of safety.
I have 4 children ranging from 23-4 years of age. Only two still live at home. I didn't teach them to be bigger children, I taught them to be adults and how to be self sufficient and that when things get hairy, call me or come home for a while.
They are taking advantage of your fears by mooching off of you. That's not teaching them to be productive adults. You are using your fears to keep them at home. That's not good either.
Give them 30 days to find another place to live and help them prepare in the meantime.