“Do I tell my wife that her lesbian daughter cannot bring a new granddaughter for a visit into our house?”
No, tell her that the granddaughter can come for a visit but not the lesbian daughter. The granddaughter is helpless and did not choose to create the situation.
How many children are they going to produce?
That does not work either. One’s child must remain one’s child regardless the transgression. If the Prodigal’s father can long for and celebrate his son’s return so must we be in constant prayer for our children who have gone astray.
Never, never, never close the door on your child. It is the burden and the blessing of parenthood to provide the kind of unrequited love our Father has for us.
In so doing do not assume you must accept the sin of the child. You must not. Hate the sin and make your hatred clear. Love the child and make that even clearer.