My adult daughter and I are planning a trip to London in early October and are considering a day trip to the Isle of Wight. We would appreciate any logistical considerations or thoughts. Thanks.
You're going to have to make it early!
What do you want to see/do in particular on the island? It's not feasible to see and explore it in a day and it also depends on how you intend to get about. The fastest way to the island is to take the train from London Waterloo to Portsmouth and Southsea station, from there take a taxi to the Hovercraft terminal and the hovercraft will take you to the island in ten minutes. From there you can either hire a car or travel around by public transport (bus is the most extensive).https://www.hovertravel.co.uk
The other option is to take the train to Portsmouth Harbour and take the ferry across either as a foot passenger or with a car. http://www.wightlink.co.uk/go/isle-of-wight-ferry-routes-destinations/portsmouth-fishbourne/
This is a slower option and eats into your journey time more however as most sites don't open until 10.00 you may not consider that you have to rush.