I wouldn't attend anything to do with that nonsense, not for a big gold clock. They have no personal credentials to be monarchs/members of a ruling family (as in they haven't done amazing or generous things). If the papers are to be believed, it's just the opposite.
They're German, anyway. They can go and be monarchs in Germany (sorry Germany, you don't really deserve that). You could see how happy Charles was with his German cousins, chattering away in his true language.
My sister's sons/my nephews are in their 40s, and they love them! Where did that come from? We were never a pro-monarchy family.