Hi- In July we got to the Canal about 5 pm, but a lot depends on their "slot". We had to wait for traffic to come through the other way. It did affect people on first sitting a bit, some went to the buffet that night. The captain's cocktail party wasn't held that day, so it didn't matter too much.
We didn't do any trips that week. We went to Olympia independently from Katakolon, certainly worth a visit even though the port area is very nice. I enjoyed it much more than I expected as the setting is so lovely. Rethymnon had plenty to occupy us for the long day there, including a nice beach.
Santorini we used the cable car and public bus to go to Oia. Athens we had done before so used the metro for a quick trip into the city- it was 40 degrees! Skiathos is beautiful, we went to the nearest beach to the left of the headland as you get off the tender, and explored the town a bit. The destinations team give you very good advice about what you can do independently, it is worth going to the independent port talks and getting the pack of information and maps, although you can pick this up from their desk. If you want any more specific advice just ask, we thought it was a fantastic itinerary,
kate