Making decisions with geeks around can be frustrating sometimes. You ask for their input, make a decision, and then (moments later), they start offering alternatives to the decision.
Hello? Did they not hear what I just said?
Well, they did hear it. But it didn’t stop their minds from working on it. And that’s what you’re experiencing when they start offering alternatives to the decision that you thought you already made.
You might find it frustrating, but, if you cannot go back on the decision, I would suggest trying to simply tell them that you’re done with the decision and can move on. Surprisingly, they usually won’t find that offensive. (That was the part I had to learn.)
You should also consider listening to them, assuming that you can change the decision. Sometimes those post-decision ideas are much better than anything that led to the decision.