I remember once in Hyatt cancun.

these people checked in ( didnt see it) but at checkout there was a charge for 2 extra people and the clients denied there were 4
and the agent bought out footage of the 4 going up to the room and coming out the next morn

there was a terrible row but the desk agent was adamant they were charging the card for the extra.

but if you are all going in very early am then leaving I dont see a problem.
also where is the 4th person going to bed down??