Great questions Sheila!
As for complete clothing changes, some do. Some do not. Some change into running short, other add a bike jersey over the tri top for more food storage options. Personally, I hate running in spandex so I always prepared to change into running shorts. Did I ever? Nope! It’s best to be prepared to if you want to and then you can make a game day decision.
Like the change of clothes, you should always be prepared to run in the dark. Thus this would mean to have a headlamp in your special needs bag. Every course is different. Some have decent lighting. Others do not. It’s hard to have lights across 26 (or 13 miles). Also, if you think you will be out after the sun goes down, I always recommend adding a light weight, throw away, long sleeve t-shirt in your special needs bag. Once the sun goes down and you have been sweating all day, it’s easy to get chilled initially. Put on the shirt and then once your body acclimates, you can throw it off as needed.
In the end, Ironman is all about being prepared for any ‘potential’ situation and managing them the very best you can. It can make the difference between a successful finish or not. Great questions!
Do others have experience on changing clothes or items to be prepared with? Please share!