First off, the warning was mainly a disclaimer. You and your friend may have a blast.
You should read the psychedelic safety FAQ.
The Hydroxyzine is questionable due to iit being antihistamine, I'd save it to the end. Antipsychotic medicine also works.
If your friend is experienced, that will help.
When you do psychedelics your mindset is the main thing.
The Hydroxyzine afaik shouldn't be a problem.
Maybe someone else will weigh in to make sure.
I have found that if you have safeguards in place, you are more relaxed going into your trip.
You probably will have a great time, but learning to have a back up plan will insure a nice time.