I'm not sure that the full €600 would be payable per person, given that the "replacement" flight got to its destination with a delay of less than 4 hours, thereby allowing compensation to be reduced by 50% under Article 7, paragraph 2 of the regulation. This strategy appears to have been followed by AF, who offered €300 in cash.

I did the free flight check on the Dutch-based EUClaim claims agency, and they have determined that the flight in question doesn't qualify for compensation due to an "extraordinary circumstance" and therefore will not even accept claims for this flight; but you will probably find another claim agency that will take up the case.