@hecallsmelove: I highly recommend having one if at all possible, even if you have to manage with just you and whomever happens to be available due to the odd time in the week, or even if it is just you, your Fiance, your officiant and the coordinator.
There are so many factors beyond what you write down, environmental issues you may not even consider now because you just haven’t experienced them in light of your actual ceremony. Of course there’s the usual: Where will everyone stand/enter, who will get them into place and when, how will they line up once they arrive in place, are they walking far or is it a short walk, where do you stand so people don’t see you before it is time for you to walk, who will hold your bouquet? But then there’s other questions like: Is there a podium for a reading or will they need to provide their own folder and if so, where will it be placed?, who says what and when?, does the place smell funny? (there were dog droppings in the garden where our ceremony was to take place the next day and thankfully we were there at the rehearsal to call that to someone’s attention so it was cleaned up in time!), liability issues? (there was a leak and a puddle forming on the grounds that was soaked up before someone slipped on it.) and on and on… It’s a good opportunity to walk around, take it all in, breathe, and be present before all the wonderful, but inevitable, distractions.
All these pieces contribute to how things will go that day and how you will feel overall. Add that to what everyone else is doing, feeling, needing, the high stakes of the event, and you have quite a lot of butterflies to settle. Consider the size of your bridal party: the more people, the more need for rehearsal. Of course, it won’t all be perfectly calm and something is bound to be slightly off, but if you can be that much more sure of it, rehearse it. Mind you, you’re asking an actor here, so I understand full well the value of rehearsal!
We were blessed with an outstanding day of coordinator, too, but even still we were grateful for the rehearsal. Gently ask your bridal party to please attend. Don’t worry about putting anyone out. In agreeing to be in your bridal party, it is only common sense that they are agreeing to assist during the rehearsal (partly for their benefit so they know what to do/where to go!) and enjoy a rehearsal dinner afterwards as thanks. If they cannot attend of course you understand. Do your best to account for them early the day of, but do as much as you can ahead of time so that you and the coordinator and everyone is free to deal with whatever else comes up. Good luck!