If you actually support the monarchy and will be celebrating the wedding?
It's easy if you have non-monarchy leanings - the fact that it is based (amongst other things) on a hereditary system that accepts a woman as queen only as the last remaining option, even if she is the eldest, is part and parcel of the whole undemocratic kaboodle. (DS is fluent in this pov by now!)
But what do you say to your Princess mad daughters, and what will you say if K&Ws first child is a girl and then a boy? "stop fantasising, dd, Princes trump Princesses"?