CAT 7 year glitch

In 2013 my wife and I bought a small house for 250k with a retirement lump sum, since then my son and daughter-in law have been renting it at the area's going annual rate minus 12k. They are both in full time employment but have recently taken serious wage reductions. I would like to transfer the property to them to try to ease their financial burden but the property has increased in value by about 200k so now they face a potentially large CAT bill.
I hope to avoid CGT if the transfer takes place before 2021 due to the 7 year exemption, but if I delay the transfer will the CGT that I then pay be allowable against their CAT?
Is there any other way to help reduce their outgoings?