1) I don't know. You found the Miyajima tide info so you can find open/close times for the sights. Am guessing that a visit to Miyajima to see the maple trees on the holiday might be a popular idea. If the ropeway is busy or closed then you can just hike up, right? (better you ...). Can't imagine the shrine would be closed. The ferry will be running.

2) I was thinking that peak color in Kyoto would be around thee 18th. My comments about koyo season may well be wrong as the japan-guide 2015 reports tell a different story.

Thanks a lot everyone for all the help and info :)