Cathy - I reserved my tickets online as well and booked for June 14th. I paid 11 euros per person (includes the 2 euro reservation fee). That reserves your tour for the underground and third ring, but it does not include your entrance fee. I e-mailed the information center and info@coopculture.it and they told me that I would also need to purchase an entrance ticket to get into the Colosseum, Roman Forum, and Palatine Hill.
I was told you can buy that tickets at the reservation desk of the Colosseum the same day of the visit, before starting the tour. I also heard that you can buy the tickets at Palatine Hill, which has no queue lines. I think I will purchase my entrance tickets the day of our tour, either at Palatine Hill or when we get our tour tickets.
If your tour starts at 9:40, I would get there at least 30 minutes before in order to get your entrance tickets.