Hi Rebecca!!
Congrats on your engagement!..
I personally never been in Isla de la Pasion...but the reviews I found on trip advisor regarding weddings were all great....here's the webpage:
http://www.diamondorchidweddings.com/
They managed everything for all inclusive packages...it includes almost everything ...food, drinks (open bar), music (DJ), waiters, the religious/civil ceremony, cake, bouquet and even photography. But then again, I believe almost all venues in the riviera use all inclusive packages.
We did not particularly liked the photos they sent us as sample, so we have booked an external photographer (William Sanchez ..loooved his work on his website). They give you an standard (base) price for use of the island, plus your number of guests...what's great about them is that you can invite 300 people or 5....there is no minimum...and you got the whole island..just for you and your guests. (I believe for Saturdays there is a minimun of 50 guests...but any other day its ok to bring less guests).
Here are some reviews I found on trip advisor about them:
http://www.tripadvisor.com/ShowUserReviews-g150809-d154082-r54271927-Isla_de_Pasion-Cozumel_Yucatan_Peninsula.html
http://www.tripadvisor.es/ShowUserReviews-g150809-d154082-r77576332-Isla_de_Pasion-Cozumel_Yucatan_Peninsula.html (this one is in spanish, they posted several photos)
Hope this helps a bit (:
Welcome and good luck (: