No. This is not considered as a "major change" that gives you reasonable grounds for obtaining a full refund. The airline can change the aircraft, and even the operator of the flight, with impunity. Their contract with you is to get you to your destination at or close to the agreed times - the aircraft type, airline actually operating the flight, choice of seat, or flight code of the flight, are not part of the deal. It is only once the ability to get you there at those times starts to shift that a "major change" has occurred.

If one of your party wishes to cancel their ticket, you should cancel the ticket through the agent that made the booking. If this was Norwegian direct, you will get most of the taxes back. If it was booked through an agency, their fee for processing the cancellation will likely cancel out any tax refund.

Or wait to see if any further changes to the ticket give rise to the possibility of cancelling for free....