Below is a Google Sheet that explains the New York State estate tax cliff and the role of the Santa Clause, which can be added to one's will, in increasing the size of the inheritance. This file is view only, but if you open it you can download it as an Excel file (under the file menu) and you should be able to log in to your own Google account and duplicate it to your account so that you can edit it. But the graphs don't translate perfectly. So if you want to use Excel you can download the spreadsheet on the dropbox link below (I don't know how to scale the graphs as I did below in Sheets).
To open sheet in Google, click on the upper right corner of the spreadsheet window below. Please send comments and feedback to j.dana@northeastern.edu.
If you determine that you want to add a Santa Clause to your will, here is an example taken from the will that lawyers created for my mother-in-law. By posting this, neither I nor any attorney is guaranteeing that this language is sufficient, nor that you should consider preparing a will with a Santa Clause without legal advice.
EIGHTH: My executor shall distribute to one or more charitable organizations described in Sections 170(c), 2055(a) and 2522(a) of the Code that my executor shall select, in his or her sole and absolute discretion, the smallest amount of property, if any, that will reduce the New York estate tax that would be imposed on my estate but for the provisions of this paragraph and reduce total applicable taxes by more than the amount of such distribution.