I think they are fucked either way in the eyes of a lot of folk, ie they are damned if they do and damned if they dont.
They arent in the forces for the money, thats for sure, so they only reasons they are potentially there IMHO are:
They want to be to help and fight for the country they love
They want positive publicity in the paper

I suspect there is an element of both those reasons, but ultimately I think fair play to them for giving it a go to the largest extent they are allowed to, in some ways they have freedoms others among us can only dream of, in others they are a lifelong slave to the rules governing the family that they were born into through no choice of their own
Genuinely not sure if I would show the strength of character they do or not if I was in the same position, must be fucking tempting to just be a playboy prince and fuck your way through every fit celebrity going etc as opposed to doing charity work and joining the forces.

Overall, I dont actually think they could possibly do much more to be good ambassadors for this country, and I think that charles in particular is a very inteligent man who genuinely does care about this country, Id actually sooner be a monarchy under him than carry on putting up with the two faced snivelling little back stabbing cunts we generally are limited to voting for after they have brownnosed bribed and cheated their way to the front of one of the two political parties.