From old Mac to new Mac - what do I do?

"I am giving my 5 year old iMac to my grandaughter but it has all my Adobe CC apps on it:

You should uninstall them if you are no longer using the laptop, as the license is for you and not her.

For more details you can refer the following link

https://helpx.adobe.com/download-install/using/install-apps-number-of-computers.html

-Manan

You don't need to do anything major. Just install Creative Cloud on your new computer, login using the Adobe ID that has the subscription and install whatever application you use. If you want to use applications on the old machine as well you can keep them else you can uninstall them. The licensing allows to use only on one computer at a time so you can use both your computer's for working on the app's provided you don't use the programs simultaneously on both the machines

-Manan