In case NCL doesn’t offer a shuttle service you can also use public transport. This means coastal tram to Blankenberge and from there the train to Bruges. Children younger than 12 years and with a parent travel with the train for free. Roundtrip for adults will set you back €7.80 per person.
For the tram your children are not young enough, so no discount here. To safe money you can buy a 10-ride ticket for €21 at the ticket machine at the tram stop in Zeebrugge, or the nearby Spar supermarket. You can use this ticket for 5 persons for the roundtrip between Zeebrugge and Blankenberge. So an additional ticket for the 6th party member is needed, meaning two times a single ticket for a single journey, wil cost in total €6. For this tapping once with your bankcard while boarding is enough, tapping out is not needed as this ticket is valuable for 60 minutes travelling.
Total costs rountrip Zeebrugge to Bruges for 4 adults with 2 children is: €58.20
The tram stop in Zeebrugge is some 10 to 15 min. walking from the cruise terminal. The Spar supermarket is just a few steps from the tram stop, but can be closed. Another option is buying the tickets online. The tram stops opposite the train station in Blankenberge, trains from there are very frequent. Trams run lesser frequent at the end of the day, but usually you can catch one every 15 minutes or so.
For more info:
https://www.belgiantrain.be/en?journey=0
https://www.delijn.be/en/tickets/