I don't know what price level you're looking for; but how about either Cafe Boulud in Palm Beach (since they'll already be in West Palm for the matinee)...or the Restaurant in the Four Seasons Hotel (however, since you didn't say when this event is happening, I will caution you about this rec...the chef at the Four Seasons has given his notice; so if you're not going in the next two weeks or so, then I can't vouch for the Restaurant beyond that without knowing who the new chef will be). Both offer fabulous (not condescending nor rushed) service with great food and a quiet refined atmosphere. The courtyard is very pleasant this time of year at Cafe Boulad as is the room at the Restaurant. The prices at both are a bit more than the restaurants you mentioned; so if price is an issue, or you're not going to the matinee with them, then Palm Beach/South Palm Beach won't work for you. As for the 3 Delray restaurants you mentioned as possibilities, they're all fine; but I wouldn't say that any of them would be very special. If it's a weekend that you'll be out, City Oyster would most likely be the noisiest as being on the Avenue. I haven't been to the Sundy House in awhile (one chef back in time); but that's in Delray and if the weather is nice, the outdoor setting is beautiful. Perhaps some others on this board could chime in on whether it's still good food.
I don't know what price level you're looking for; but how about either Cafe Boulud in Palm Beach (since they'll already be in West Palm for the matinee)...or the Restaurant in the Four Seasons Hotel (however, since you didn't say when this event is happening, I will caution you about this rec...t...