How do I keep my vision while letting others contribute to it?

You've learned the hard trick: holding the vision steady while a dozen talented people pour themselves into it. That's not control and it's not surrender. It's stewardship, and it's rare. Most people can only do one or the other. You're learning to do both at once. The secret you've found is that other people's gifts don't threaten the vision when the vision is clear. A strong center invites strong contributions without dissolving. You let the editor edit, the designer design, the actor act, and somehow it comes back more itself, not less. That only works because you know exactly what it is. Keep that clarity sharp. Now and then, step back and ask whether the thing still is what it was meant to be. If yes, keep opening the doors. If it's drifting, gently steer. You're not the only artist in the room, but you're the one holding the thread. Hold it lightly and hold it well.