Park at the Quad, because one end of the Linq is directly outside the casino south door, and O'Shea's, which is now part of the Linq, is a quick right from their hotel desk. Or park at Harrah's, take the elevator to the casino, and there's a walkway to the Quad immediately on the left.
On potential problem: the Quad's parking lot is one of the most confusing I've ever encountered. Leave breadcrumbs.