Keeper keeps choosing the safest short pass

Yes, I’d encourage it when the picture is clearly there. If the goalkeeper can pass beyond the first pressure into a free midfielder, that can remove two or three opponents from the next action. The technical challenge is receiving that pass well enough to use the advantage. I would not tell the keeper to break a line just to prove they can. Set up a game where the defenders and midfielder move against a pressing team. Sometimes the safe short pass is best; sometimes the midfielder is free. Then ask the keeper: “Which pass gives us the best next action?” At U11, a goalkeeper who scans and occasionally finds the line-breaking pass is developing well. Safety and bravery are not opposites. The decision should come from what they see.