I'd reconsider doing any type of tour since you'll be traveling with a baby. They get bored of watching buildings and just going around in their stroller. We just came back two days ago and we travelled with our 2 1/2 year old daughter.
We took a stroll around Messina, there isn't much to see. If you've never been to Taormina, go, because it's just gorgeous. There is a little playground in the public garden and even a few parrots in cages where your daughter can have some fun after you go around the town.
We then went to the zoo in Rome and the aquarium in Genoa. My daughter is older than yours though, so she appreciates these things a bit more i think.
Barcelona was in the afternoon and she slept most of the time there. We walked around a bit but didn't want to see it so we wouldn't spoil the surprise when we go back this summer. We shopped around at MareMagnum too.
She loved Sidi Bou Said in Tunis, she likes the colour blue so maybe that's why. We went there by taxi.
The tours on the ship are so expensive. They're not all a day long, some are just four hours so don't worry about that. Booking organised tours does take the headache out of figuring things out on your own though.
thanks for the info, we were thinking of going down to all ports... or maybe using the hop on hop off buses as the timit is a bit limited to go round and maybe booking a tour for rome as i read that the port is abit far to rome. what do you think of the other ports? Is it easy to travel from the ship to the ports and to the other cities visiting? another thing please, in what cabin were u? I booked an outside cabin but with no balcony, should I go for the upgrade?