Hopefully a simple question ... flying JFK-LAX-MEL in business on a single ticket, JFK-LAX on DL and LAX-MEL on VA.

I understand the lounge access in LAX is the Emirates lounge at TBIT. Does Virgin use any sort of lounge invitation card, or will a boarding pass (presumably one printed on Delta stock at JFK) suffice at the Emirates lounge? Just wondering if we need to stop by a VA check-in desk at LAX or if we can use the airside shuttle and go straight to the lounge.