I think you need to be very explicit about how you would help them. I’m imaging one scenario where they are going to this school (are they both currently enrolled?) not because it was their first choice but because the tuition would be free to them since you are an employee there. You quit the job to take a higher-paying job elsewhere, leaving them suddenly responsible for tuition at a school that wasn’t their first choice. You get 20k more a year while they rack up debt they weren’t expecting to have (again, at a school they potentially would not have chosen for themselves if they knew they’d go into debt attending it).
I think as a daughter, I’d be pretty hurt and upset to be in that position. If I was going to have debt anyway, I’d have preferred accruing it at a school of my choosing. If my mom left a job that gave me free tuition to take a job elsewhere for more money and she didn’t use most of that money to help me with the tuition I was suddenly and unexpectedly responsible for, I’d be pretty pissed off. So, if your intention with your extra 20k a year – aka “financial freedom” is to pay your kids’ college tuition with it, please let your daughters know that.