In all things--PLAN AHEAD, don't prepare for stragglers, prepare for your success in your best interests.

Your instincts are correct in wanting to have someone to ride "Shotgun". Work it out with someone to partner up in your retreat. This person should also have a fully equipped Bug Out kit. This person should be able to help you and vice versa.

Since there are so many people you know that don't have a vehicle you have a great bartering tool, they get a free ride to safety and you get someone to do some driving and security, splitting the expenses.

I would not rely on picking up someone(s) that you do not know to help you in any way. They most likely have nothing that you need for your trip/retreat and will probably be mooching off your equipment.