No one ever asks you to onboard a new team when there is nothing to do.
It’s not a thing.
There is always pressure.
Always the need for it to have shipped yesterday.
So now that you know what you’re up against, build a plan that onboards your new team taking into consideration all those emotions that they are feeling. Reassure them that they will get there, listen to their feedback, count to ten, whatever it takes for you to stay calm and get things working with them.
If they are super green, they will have no idea what Agile, refactoring, patterns or practices are. That’s your job, you’re the leader, show them the way… just like someone showed you when you were starting out.