Thunderroad

I'd say plan on not getting the complimentary upgrade upon check-in and be in for a pleasant surprise if it does happen. Which means that if you think the upgrade from what already sounds like a very nice suite is worth what the WA is charging, then spring for it.

Like you, I find the WA Reservations agent comment that they can't enter additional info in your record odd...actually, almost unbelievable for any hotel, not mention one of the WA's supposed stature. I'd call Hilton and perhaps call back the WA, as they should be able to enter info about this special occasion in your record (and, while they're at it, enter into the record a polite request for an upgrade if possible--it can't hurt to ask). That in turn might translate into some kind of a pleasant little perk for you and your wife, albeit probably not an upgrade.