As far as I can tell, the players state what they're doing, and the GM calls for rolls as appropriate.
Obviously at a table, there will be some back and forth.
GM: "That sounds kind of dangerous. Give me a Defy Danger pluuuuuus..."
Players: "Str!" "Dex!" "Wis, it's about him noticing the ledge."
GM: "Sure, lets go with Dex."
Player: "I try to puzzle this out..."
GM: "Cool."
Player: "What do you think? Is that a Discern Realities?"
GM: "Oh yeah! Gimme a roll + int!"
I'm not surprised at your Newbie/Experienced player story. I'll never forget the looks on the faces of my players when a first time roleplayer rallied a village to come and help (they never thought of it because of preconceptions - clearly the heroes have to solve all problems on their own!) Playing these games sometimes damages our capacity to roll in the fiction, and that's what the players should be doing: putting down a story together. The game's pretty robust. It can handle most things. Thinking inside the moves as your only options frequently stymies it.
If they look up, and wait for you to acknowledge a move, just do it. It's cool. The book gives you permission. Don't let it rattle you. It's just part of the back and forth.