OsakaWino

As MikeFromTokyo said, they're usually quite willing to guarantee and upgrade to a Deluxe Room or Park Suite (and probably also to an Executive Suite) for the difference in the HDR from the base room, but I'm pretty sure you have to contact the hotel directly to do this, although maybe an FT concierge can contact them for you.

If attempting to contact the hotel directly by email, I suggest getting a direct email address from someone. For our first stay I used the generic email on the hotel's page and the reply I got was from Europe central reservations and the requests I sent them were never forwarded to the hotel. For our second stay someone here on FT gave me the email address for the GM and he was incredibly helpful.

There have also been a few posts reporting upgrade available at check-in for a lower amount than the difference in the HDR, but I guess that's not a good option when your sending your parents on a Guest of Honor booking.