I have a guest that has booked my house and he has people arriving before him and has asked me to give them the keys?
Should I do this? Or should he be present?
If they are part of the group then it is not a 3rd party booking as long as he is staying too. I see no reason if you are comfortable with the booking not to give the keys to whoever arrives first. Otherwise you will risk negative reviews if you leave people hanging around waiting to get into their accommodation.