Since there are going to be many members of the Olympic Committee going to PA's wedding, it's possible that Princess Anne and her husband will go.
I loved reading your post because I totally forgot about Princess Anne and her extensive background with equestrianism, even competing at the 1976 Summer Olympic Games, but more importantly being the President of the British Olympic Association!
And that fits in nicely with Prince Albert being the President of the Monaco Olympic Committee.
On that basis alone I think it would be apropos and lovely if she and her husband were able to attend.
By that same token, I think it would be equally lovely to have Athina Onassis and her husband, Doda, attend as well, based on the fact that Doda is a two-time Olympic Medalist in equestrianism, as well his wife is a friend of Charlotte Casiraghi, both touring together on the Global Champions Tour. Not to mention Prince Albert was Honorary President of the Jumping International de Monte Carlo until his niece, Charlotte, took over this past year, and who will also now be editor of GCT's new magazine.
And to go even farther back, Athina's grandfather, Aristotle Onassis, attended Rainier & Grace's wedding back in 1956, and even gave them a yaht as a wedding present!
How wonderful if the aforementioned people were invited to the wedding, I can't wait untilt the official list comes out.
ps: regarding music, I've been having a pleasureable time finding little bits and pieces I think would be lovely to have at the wedding, like Debussy's classic "Reverie":
YouTube - Gordeeva & Grinkov (RUS) - 1994 Lillehammer, Figure Skating, Exhibition Performances