I've never seen an invited guest line at a CET property. CET properties have platinum and diamond card holder check in lines. If you have one of those cards, you can use the line.
Unless your offer specifically directs you to do otherwise, you use the line for your card status. Diamonds and 7Stars have a check in lounge and Gold and Platinums have designated lines. At Rio, Platinums seem to get directed to the lounge at lot.
I agree with the others about the CET props. There isn't an "invited guest" line. The lines (or rooms) are for 7 Stars, Diamond, and Platinum at some. Even when I had comped rooms when I wasn't diamond, I couldn't use the diamond line. At CET, it's not wether the room is comped or not, it's your card tier level. Enjoy the trip! diane