Hi Kayleena,
Since a lot of people are talking about Tulum I thought I'd mention this eco place that I stayed at a couple of years ago. They have 3 properties right next to each other, but not on top of each other. I stayed at Cabanas Copal, and I totally loved it. Each property is small and two of them (Cabanas and Zahra) are electricity free (the common areas and restaurants have electricity, but the rooms don't), but they do have indoor plumbing so it's not completely rustic.
I'm not sure if they do all-inclusive deals, but here's the link to their Group/Wedding info page: Tulum | Mexico Accommodations | Riviera Maya - EcoTulum Resorts & Spa - Eco friendly Mexico Vacation Hotel – Caribbean Villas.