I believe the Wyndham website specifically notes that the rates are only good for two people. If you're bringing more than that to an all-inclusive -- any all inclusive -- you have to make sure what you are being charged. Sadly, these properties tend to be very good deals for two people but not such good deals for more.

As far as status being recognized, it seems like Grand Palladium does sort of recognize your Wyndham status but not in a predictable way. Tell them you are a Wyndham Diamond and maybe you'll get a better room, and maybe you won't. But it's an all-inclusive, so the recognition benefits are modest -- fortunately, everybody is already getting a lot of stuff included! Personally, I would highly recommend Palladium's TRS Coral in Costa Mujeres as a Wyndham award redemption. It is a good deal at a very nice all-inclusive. Equivalent, perhaps, to Hyatt's Secrets or Dreams properties.