I would suggest doing it onsite as well. Transporting in a cambro might risk overcooking the shrimp. You could speed things up by pre-heating the water and getting it there in insulated jugs. Then you could just throw it in the pot and add seasonings, get it up to a boil, and be good to go. And it makes for a much better presentation as well, IMHO
We've done this at tailgates for 50+ and it works just fine