Your kids will have to refile their tax return to include the tuition and the transfer. I'd recommend filing your taxes before the deadline to avoid potential penalties. You can adjust both your kids and your tax return after filing.
Once you have an NOA (Notice of Assessment) for you and your kids, they can add the tuition to their return and the transfer to yours. Then refile all the returns.
In this scenario, you have two options: 1. your children can transfer their tuition amount to you, their parent and 2. your children can amend their tax return and complete schedule 11.
Option 1: For tuition amount transfer, follow the steps outlined by the CRA here.
Option 2: Your children can follow these steps to amend their tax return and complete schedule 11.