You should be ok with the 2nd car at Aulani, but you may want to call to verify. This is from their website:
Parking for Disney Vacation Club Members and RCI Members
Disney Vacation Club Members can enjoy convenient self-parking at no daily charge for up to 2 vehicles. Here’s how it works:
If You Booked Using Your Vacation Points: You’ll automatically receive self-parking at no daily charge.
If You Booked a Vacation Rental Through Member Services in a Disney Vacation Club Villa or Studio: Please provide your Disney Vacation Club Membership Card information at the time of booking. When checking in at the Resort Front Desk, be sure to show your Membership Card and corresponding photo ID for validation.
(If you booked through the Disney Reservation Center, simply show your Disney Vacation Club Membership Card at the Front Desk to have the parking charge removed.)
If You Booked as an RCI Inbound Guest: You will receive self-parking at no daily charge.
Policy: Disney Vacation Club Members will not be charged an overnight parking fee when using their Membership to stay at a Disney Vacation Club Resort, regardless if they paid Vacation Points or cash, as long as their reservation was booked by Member Services or online at disneyvacationclub.com. This is also true for Guest-of-Member reservations and RCI Inbound Guests. Members also will not be charged an overnight parking fee when using Vacation Points to stay at an Aulani Resort hotel. This is also true for Guest-of-Member reservations. Disney Vacation Club Members will be charged for standard overnight parking when staying on a reservation booked through a
travel agent, the Disney Reservation Center or disneyaulani.com.
Enjoy your trip.