Considering if you think about it. He wont want sex 24/7. You WILL get chill time (& if you feel you arn't getting it, make sure you do)
I'd only really charge max ?3000 for it. Anything else would be cheeky. It's different with a holiday but of course up to you & how comfortable you feel with this guy aka how much it feels like work. Of course any client can turn bad but it's up to you. I never drop my rates but given the circumstances it's only ever debatable then. Hey, it's much more luxury than what i was offered, a caravan trip to cornwall for ?500. No.
Of course it wont feel like a full blown holiday, you will have to give sex on demand within reason & chitchat even if you feel you want to wind down so don't get too excited but it's new territory so just go with the flow & make sure he pays you up front else refuse to go anywhere with him. If he tells you he will pay you after the holiday because that is when he gets paid. I don;t care how much you trust him. Don't do it. Ever.
When on holiday remember you are still on the job, so preen yourself in the morning even just a little to be believable, keep the fantasy up & all that jazz.