The Wales kids gave clearly been trained for the events and they've carefully assessed when each child is ready to "go public" and found suitable events. They sit still in church, they know how to behave in more relaxed events such as the very long coronation concert (and all the family helped each other out with all the kids and it was delightful to see the cousins relationships).I feel it would be unkind to force 2 children of very tender years into this situation. They have no comprehension of people on this scale never mind the pomp and ceremony and the expectations there will be of them. The Wales children have been exposed to this and know what to expect and how to behave and still manage to go rogue on occasion which is perfectly understandable. TPPOW and KC, QC and the Middletons all deal with this gracefully, calmly and without drama or hesitation and this is borne out in not only their reactions but that of the children because there is a rocksteady relationship there.how on earth could it be expected that these 2 unknown children could receive the same treatment and be thrust straight into the dynamic when they don’t know the people they will be surrounded by. Even Uncle Mike took turns in entertaining them all at the PJ to great success!
For 2 very young children (younger than the Wales kids were ever allowed in public other than the ToC balcony appearances) with no training (you just know they won't have) to do all that in public surrounded by a lot of strangers with 2 very stressed (likely high) parents is not a mix that will work.
There will be shots of them playing up and parents trying to deal with it and it will be unfavourably compared to Catherine handling of Louis at the jubilee concert.
Hell they could even contain their own behaviour at the jubilee or funeral so how can they deal with their kids too?