There's nothing inherently "Adult Content" about the Horizon's adventure minigame. All-ages content like this should not be locked behind an access wall that Child Avatars are now blocked from accessing.
If having A-rated regions abutting non-A-rated regions is an internal content management concern, relocating the 6 region island might be an alternative approach.
Relocating these regions from direct-connection to the Horizon's sub-continent could also allow for better connectivity between the N, S, E, and W road systems, as well as possibly creating a location to offer a Bellisseria-style "Fairgrounds" for public reservation for Adult-themed events.