Okay, I've been out and about discussing the event with some very good people and they had some interesting insights into the adult entries.
We all agreed that it would be terrible to have a palace with incredible room art be left out because of the type of palace that it is. As I have said before, if they want to join go for it.

It was suggested that instead of the palaces advertising what sort of adult palace it was simply going with a generic sort of 18 and over palace that way it's not drawing so much attention to the lifestyle that a much younger palace goer may be more curious about it. Downplaying it. With the ideas of hubs and docks and things that have been done in the past I believe this can be achieved. On enter gates requiring birthdays and so on shouldn't really run too much into the event. But perhaps the adult palace can have those on enter/birthday required gates to deter wandering youths. Kind of like the whole cattle chute idea....I know it's not a flattering image but if you approach it something like that to keep everyone on track. That way if someone should wish to wander those age appropriate can and those not well they will either do the math to get what they want or simply go on to the next place. Everyone can enjoy the artwork and those that are concerned with keeping it so that if there is a child touring or just peering over Mom or Dad's shoulder there are not any unseemly displays or awkward questions to be answered could be comforted by knowing that some sort of safeguard is in place to protect their youths.

Keep the ideas coming. If you don't want to post them yourselves discuss it with me or someone else and I'm sure we'll be happy to bring them in here to mention.