Things to see in Ashdod
Here is my recommendation; particularly for Christians. I would engage a private guide. I would do a similar tour on the first day seeing all you can in Jerusalem. Going to Bethlehem is hard and time consuming so I would skip unless mandatory. The tour of Jerusalem would be fantastic. Then, I would drive the two hours to Tiberias and spend the night there. You aren't missing anything driving at night. Besides, no night clubs are really open Friday night if you were staying in Jerusalem anyway. The next day you could see Mt of Beatitudes, Capernaum (St Peter's house), Tabgha (Fishes and Loaves), Nazareth (Church of Annunciation) and maybe a bit more before heading to Haifa to join the ship. The problems with all the Churches are the opening times. However, if you are already in Galilee and see those three sites before 10am, you can probably add Cana to see the Church for the Wedding Feast before having a quick lunch in Nazareth before sightseeing.
If you don't want to spend the overnight, and you don't mind a couple of one hour bus rides, I think the Regent tours should be sufficient.
Marc's guide company:
Travex -- Conact: Ann Hillel -- email: email@example.com