According to the tour description we meet at the hotel at 5, orientation walk and then dinner. Would there be time after dinner to attend a pub crawl?
Probably. In fact, your guide may well suggest it!
if that is your arrival day, I doubt if you will stay awake.
If you are talking about an organized pub crawl that you are paying for ahead of time, no, I would not do it. I would enjoy the group I just met as long as possible, then go rest for the first full tour day.
You've got an early start in the morning for the first full day of the tour. I would recommend being fresh and rested. A pub crawl would definitely give me a disturbed sleep and might make me forget things discussed in the orientation.
We are coming in a day earlier. Our flight gets in at 4:30am :-O