Upgrading plan after final payment

[12disneybee]

My trip starts 9/6, If I were to want to add another person (villa can accimodate 8 and right now we have 6)and upgrade from TS dining to DxDP, what's the latest day to do that? Thank you.
Does anyone know a link that I can find this answer that is official by Disney? Thank you so much in advance.

 

[HeidiGW]

I think it is three days, but I'm not 100 percent.