This is a confusing post. Are you actually staying at the hotel in a guest room?
Although whether you are or not, you're asking for something that is not part of Marriott's frequent guest program perks. The program clearly states that you get complimentary in-room internet access. Thus, providing internet access for your car isn't something guaranteed.
Hotels with meeting space tend to lock down their public internet access because they charge groups to use it. That's probably why this is being referred to as a "conference" password.
As an aside, maybe I'm a Luddite but I don't understand the need to monitor dash cams in a parked car.