Gary,
I think you’re trying to give “openness to life” a narrower definition than the Church does.
Here is an analogy that Dr. Douglas Bushman gave that helped me with this whole thing:
Imagine that a married couple’s sexuality is like an ice fishing house (you know those little shacks that people put on a frozen pond that has a door, walls, a roof, and inside has little benches around the walls where people sit while they fish through a hole in the ice on the floor).
God has given you this fishing house. He designed it and explains to you how it works: Any time you and your wife want to “go fishing” at the fish house, that’s fine. Go in any time you want. However, about 3 days a month (when the wife is fertile), God is going to enter the fishing house. If you choose to go fishing in there while God is there, He may exercise His creative power and give you a child. If you happen not to go fishing during this time, no child will result. However, God simply asks that you keep the door open to Him. He never makes you go in, and he may not choose to give you a child if you go fishing while he’s there. But that’s his prerogative.
Now, how does this [imperfect] analogy play out?
If you are a couple using NFP, you keep a calendar and can reasonably predict when God will be present. On those days, you stay at home. God comes into the fish house for a few days and then leaves. The door has remained open for him.
The contracepting couple would be a couple that goes into the fish house and locks the door shut. God tries to enter on his days, but can’t get in because the couple has willfully prevented God’s entrance while they are there enjoying some “fishing”. He knocks, but they don’t enter. God may try to breakthrough the door (eg. contraception may fail), but the intent of the couple is obvious: enjoy the fishing but not let God have his creative option.
The pregnant couple is also not locking the door. They go into the fishing house as God intended it. However, God chooses not to enter because he has already exercised his creative option. The couple has not placed any barricades to the door, and neither has God.
Finally, the post-menopausal couple is where God chooses not to enter the fish house anymore, but he leaves the door open for the couple to continue to enter as often as they want. He has decided he is done visiting (for procreative purposes…of course God is present in any act of love to some degree) . The couple is not shutting God out by a willful act. This is God’s decision.
It’s an imperfect analogy, but it gets to the heart of the matter.