Shore Excursions and Travel Insurance

Should you count the cost of shore excursions when determining amount of coverage? My understanding is that they are not considered a common carrier ( such as an airline, cruise line, etc.) and would not be covered if your private tour vendor did not get you back to the ship on time.

Only if the excursion is pre paid and non refundable.

You are correct that if the private excursion bus breaks down, the bus is not considered a Common Carrier as defined by most if not all insurance carriers.