The Big Bus tours are promoted by the ship but in the arrivals hall Citysightseeing were offering something almost exactly the same but much cheaper. They were very negotiable on price and we paid AED 180 for a 3 day pass. Unlimited water was available on board. Allow up to 1 hour for the shuttle to get to the main hub at Dubai Mall before you can start your tours. On the beach/marina circuit ...
Dubai is nice, we didn't take an excursion, you'd better do it by yourself. We took one of the hop on hop off busses. Be aware that MSC also sells these tickets (also in the cruise terminal) and for just one day, always starting at 8 A.M, also if you start in the afternoon. If you buy the ticket at the bus, you get a ticket for 24 hours starting at the moment you really start your tour. ...
We have been several times before, so used the shuttle bus which was horrendous. The Mall was fabulous but with over an hour wait and total confusion with the Hop on/off buses it was a nightmare. ...