As an alternative to staying in Rome, I would recommend staying at La Posta Vecchia. It is about 30 miles north of Ostia. I would spend the day exploring Ostia Antica (a mini Pompei). The hotel can arrange a guide for you. The restaurant is also fabulous. If this is to expensive there are many hotels in Lido di Ostia that are very reasonably priced and right on the beach. This is a popular Italian vacation spot in the summer. Benefits - close to airport/cruise ship and beautiful ruins without the hustle and bustle of Rome.