Hi David
Congratulations on your forthcoming wedding, you've picked a great spot for your honeymoon.
I don't know about trips to the Greek Islands but there is a travel place just off the main square in Hanioti which arranges day trips etc., including boat trips to Mount Athos to see the Monasteries (sometimes dolphins follow the boat), various cruises - fun and sunset etc also trips to the market and all sorts.
Pefkohori is a nice walk from Hanioti along the lower road (the beach road) and there is a nice bar about half way along with a lovely garden right on the beach. Depending on the heat and how fast you go, it should take about 45 mins.
We're going on 24th August for 17 days for the 11th time (we do go elsewhere too) and love it because it's so chilled.
Enjoy.......