Well to be honest I would've expected their attendance regardless... Only time will tell I guess.
No,why?It happened before,also during Juliana's Reign,that the Heir was not present for one reason or another at such occasions,
so its nothing new.I think what some believe/think they have to do is not always that what they have to do.
Besides,considering the heavy duty calendar (past and ahead) they've worked through over the past few weeks alone,and the subsequent time they've missed out with our lovely triple A's,grant them more then one reason to have a few days off,Fall holiday/Herfst vakantie as we call it.HM is perfectly OK with it,the President is OK with it,and that is all that really matters.
IIRC the President and PWA and Máxima already met as the first visit abroad of Máxima as Princess of The Netherlands was to Ghana.
Princess Margriet can not attend as she is in Johannesburg for meetings of the African Red Cross & Red Crescent.
I checked the school holiday calendar too,but as Amalia doesn't apply to that rule yet,she's too young,well,untill this december 7th when she will turn 5 that is.