Tricky one. They might be happier in Chelsea / South Ken where the hotels are more 'old school' and they would be walkable to the V&A and other museums - somewhere like the Cadogan Hotel or many of the others in that area.

Shame the main Four Seasons is closed, as this is the sort of occasion when there excellent customer service would be valuable.

Covent Garden is horrendously busy these days (so busy that the tube station is 'exit only' at weekends) and it would be very easy for them to be rushed off their feet.

Perhaps one of the Park Lane places would do. They can cross the road into Hyde Park and take taxis everywhere else. Browns, as mentioned above, is not a bad choice either.