Here are a few of the templates I use for vacations and backpacking trips that help me stay organized and collaborate with my fellow travelers.
Make a copy of the google sheet template adjacent if you want a more complex and thorough plan for your trip. This template will allow you to plan by the hour, include you're legs/transportation, and help you budget using a form response collection. Personally, the form responses became a little cumbersome for me but it was super helpful to keep me accountable when I remembered to fill it out.
Another template I like to use is just a simple notes app on the iPhone. If you're going on a quick trip and want to share it with others a quick notes itinerary is usually the way to go. Plus, super easy to make a collaborative note itinerary if your friends also have iPhones! If they don't have iPhones, well then why are you going on a trip with them.
All in all, it's always a great idea to have some type of itinerary when planning a trip. Like I always say, it's better to be bored now planning then bored then when you don't know what to do. Oh, and don't ever be afraid to stray off the template... often the most enjoyable parts of the vacation are the ones you can't plan.