From this distance its difficult to tell because I do not know all the facts.
In order to be eligible for capital gain treatment, the asset sold has to be a capital asset. A capital asset is generally an asset held for personal or investment purposes. Generally, assets used in a trade or business or property held for sale to customers (or will become property held for sale to customers) or property acquired in the ordinary course of your business, is not eligible for capital gains treatment.
A contract for a right to develop implies that you are in the business of developing real property. If you originally acquired the contract in order to develop the property, if your trade or business is the development of real property or if your contract just refers to the right to develop and does not represent ownership of real property, all these things will swing the character of the gain in your hands. Based on the above I suspect your gain will likely be ordinary, but its an educated guess not based on all the facts.
I really believe all of you should engage a qualified professional who can get their arms around all the facts. This will allow a more thorough analysis of your situation which should result in at least your making educated decisions about how to proceed. With $1.8MM at stake don't pinch pennies, get some real professional help that yo can sit down across a table from.
Also, while FL does not have an income tax, obviously NY does. If your a resident there, they will also tax the transaction.
Because it is impossible for me to identify and consider ALL the relevant facts, this advice is not intended or written to be used for the purpose of avoiding penalties, and cannot be used for that purpose.