We talked to our server about this when we dined there Monday night. They really do not check who is coming and going, so it is possible to get to the observation deck without dining at CG. I can understand why they can't really control it. Monday night was fireworks night. We were lucky enough to get the LAST MK view window seat. We had arrived around 7:00, and were seated around 7:20 even though we had a 7:50 PS (I think they worked us in because it was my birthday). When we had arrived at 7:00 there was no one in the lounge area while DH and I had a glass of wine before dinner. After we got seated, probably around 7:30 the place was MOBBED. People every where. In the lounge, right by the bar, at the hostess check in area. People for as far as the eye could see. So, there is no way, they can really know who belongs there and who doesn't. lol
There were some nice tables by the windows in the lounge area, but like I said, the place fills up fast.