Maybe it depends on the hotel, but typically lounge access is coded into the room key card. While I don't recall testing this by having someone else check in first, I would certainly hope you wouldn't have to get new key cards when you arrive at the hotel. Perhaps have your partner ask at check in if lounge access is on the card or if you'll need to get new cards? This will result in either 1) desk clerk ensuring access is keyed in or 2) explaining you will need new cards. If 2, then she can ask if it's possible, as a one time exception, to key the access because you'll be arriving late and don't want to stop for new keys. Worth a try.