In my opinion. If you are in a wedding party I would avoid wearing an Apple Watch and switch it out for something a little more timeless. I know when I take photographs of people I make them take their AW off just so it looks a little more timeless. A big computer on your wrist looks silly. But if you aren’t being photographed then AW is fine.
I wear an ultra all day long but if I’m in a formal party it’s being switched.
As someone who is just starting in photography and mostly shooting friends. I would 100% send you the money back if I cannot commit to a day. There should be no reason why they shouldn't, especially if they canceled on you. I had to cancel on a coworker because of work and they 100% understood and we made plans for a week after.
Communication is key and they obviously struggle with that.