I would add it sooner rather than later! You will end up with a tougher crust (from overmixing), but easier to incorporate when it's more rather than less pliable. Personally, I would start over.
Thank you :/
I suggest you make another batch with the correct quantities for the pies you will be serving to party guests.
I'd freeze the incorrect batch for another time and possibly for a dish that isn't as sensitive to the properly seasoned crust (like cheese twists or something else).
Great advice, thank you. I've already made a second batch. I'll freeze the first for something else.