If there's something that's critical in your plan, always prepare a backup.
Imagine something happen to you, make sure people know who's your backup. That's the person they'll to talk to if you don't want everything to stop until you're back.
Imagine the people you count on are suddenly not available anymore for some reason. It might not be easy to replace them unless you have a backup plan. This can be within your team or outside with freelancers.
Take a little time now to save a great deal of efforts later on!