Brainstorming...

its easier to start a middle then it is a beginning, because we think deeper in the middle, the beginning has too much pressure on it. it will come. sometimes the beginning of a middle can become a beginning in its own right or write even.

good luck in your writings

As Castle said, sometimes middles turn to beginnings, and what would have been the beginning is revealed through dialogue or well-placed backstory speels/flashbacks.

Though, if you want to work with your suggestions, I think that maybe a phone conversation then a face-to-face discussion could work best. Maybe they are trying to avoid conversation about Mark, trying to have light conversation when Owen comes out and says something like, "I think we should get out of here, Marie."

As for a first chapter start, I don't know exactly what is vital to the story, or what you want to reveal through snidbits later on in the story, but the strongest option that you have suggested is a dream. You always need to 'hook the reader in' as the saying goes, and I think that you would have the most mobility with a dream out of the suggestions provided.

Hope that helps, though the decision making will be left in your hands.