I can share some of what I have discovered through this whole planning process...although I am no expert as we haven't had our wedding yet!
Sashes and white table cloths are included, also, the coordinator sent me the list of colors like MrsNova said and then I asked "what about purple" and she messaged me back saying yes they had purple and sent me the picture of it, so just clarify clarify clarify and you will figure it out!
There is nothing arch-wise or huppa unless you pay a whole lot more, but there's always the option of the gazebo if that interests you, I chose the Barcelo almost solely based on their gazebo lol!
For centerpieces, there is a pdf they send you with their options and prices on it, they aren't too badly priced I guess but they do add up if you are trying to stick to a budget, and they do charge for all the orchids and calla lillies and such that you may want. Another option is to do like someone else on here did and rent their vases for $5 each and then bring your own fake orchids down with you to have them submerged. There are TONS of options for centrepieces if you don't want to pay their prices. If you give me your email I can forward you on the centrepieces thing they sent me.
Also for flowers they charge for corsages, bouquets, boutineers other than for the bride and groom (for the strawberry package anyways)
As for ipod or dj - we are going with ipod as most brides on here suggested that and its a big savings!
One other thing that I have heard is extra are the lights on the trees, $5 per string apparently.