I know Charles is the next in line, but I cannot help feeling that employing the younger set, Cambridges and Harry in the more prominent countries would have been a better choice. We will only hear more complaints and comparisons between dutiful present Queen and then Charles and how it is a better idea to abolish monarchy after HM passes away. I feel that W&K or PH would not garner the same reaction, in fact they may get the opposite reaction.
Last time PC visited Canada, there were articles talking about how great it would be to have a King Harry, and I don't think he's ever visited Canada or New Zealand. I think he's gone to Australia, but don't know if in any official capacity. The best strategy would be to get the three to the countries where Republican sentiments are high.