My experience has been that if the officer can obviously determine whether or not an occupant of the vehicle is pursuing or actively engaged in the searching or collecting of reptiles, he will hold them responsible for having a license.
One of my favorite police saying is "You may beat the rap, but you will not beat the ride" holds true here. Basically all the officer has to do is say he observed "whoever" looking for reptiles and he can cite you, then you either pay it or take it to the judge. In most cases the judge will believe the officer unless you have some pretty compelling evidence to the contrary such as Blindness or other handicap. Do not get me wrong I am not making fun of the handicapped, I am mearly making a strong point about the type of evidence you may have to produce to argue the point.
I guess the old addage "better safe than sorry" holds true here. Why take a chance of ruining a whole trip trying to save a few bucks. The money is supposed to go toward the "hunting and fishing" sportsman anyway. As easy as it is to get a license at any Wal Mart, I say stop the debate and quit your bellyaching and just buy the license.
ECT