Possible Clues:

• Parent whose kids have moved out
• Parent whose children have left home
• One who can finally stop postponing that long R.V. trip, maybe
• Parent whose kids have moved out, and a phonetic clue to parts of 17-, 25-, 35- and 48-Across
• Parent whose children have grown up and left home
• Macaw, Tern
• One whose "chicks" have flown?
• One whose 'chicks' have flown?
• College freshman's parent, perhaps
• One with a new guest room?