MSC Divina Ship Excursion Advice for Mykonos and Santorini

[RavenCruiser]

We will be on the Divina for a Med cruise starting May 17 in YC.  I had previously commented on the very small number of excursions available at the various port calls, generally just three to five at each stop.  I am considering the Delos excursion in Mykonos and the Best of Santorini excursion in Santorini.  I was a little surprised that the Delos tour says, "you will return to the port on your own by shuttle boat".  I had assumed we would be returned to the ship as a group.  My concern with the Santorini excursion is the eight hour length. 

 

For context, we will be in Mykonos from 1PM to 11PM and Santorini from 8AM to 6PM.  I greatly appreciate any thoughts you may have if you've taken either of these tours.  Previous comments had said it was unlikely that additional excursion options would be available once we've boarded the ship so I'm going on the assumption the limited choices provided beforehand are all that I can choose from.  Thanks in advance.