If I were just getting off a cruise I think I might like something other than a port city (no matter which sea it was on).

You can really go anywhere in terms of flights (well, almost anywhere). What would be important to me is pleasant weather so the toddlers could run around outside a bit, but also something of interest for the adults. I don't see Beligum on your list of places you have been, but it is better in nicer weather months. You might enjoy Sevilla if you have never been and the weather isn't too hot for your time of year. How about Vienna?

You arrive and depart from Rome? I wouldn't go to Vienna and back. I'd go further south in Italy, on the coast.

I think the cruise departs from Rome and returns to Rome -- but after that I am not sure they need to return to Rome.

One thing travelers to Italy discover is that it is more time consuming to get to someplace like Positano (maybe especially if you are starting from Civitavecchia, then it is to go to the airport and fly someplace else.

Again, I would just want to look at something other than a sea view and be surrounded by yet more cruise ship tourists. But I've never taken a cruise so maybe people who take them can't get enough of either.

The cruise departs and returns out of rome (Civitavechia) but we will be spending a few days in Rome afterward as we're travelling with other who have never been. Thanks for the suggestions, Malta or Tunisia seem like great options and definitely not somewhere we would really plan to go unless we just happened to be in the general area (flights to Europe from canada being what they are and all)

Malta is perfect with young children. There is plenty to see for a few days and it is very relaxed. The Maltese love children so eating out will be easy even late into the evening. Visit Mdina, the Blue Grotto and enjoy some beach time.

Regarding Malta, I'd also recommend the fishing town of Marsaxlokk, especially on market day, Sunday if I remember correctly.

The capital, Valletta, is a very beautiful and entertaining small city, with a pedestrian center.

Also, I didn't see what time of year you'll be traveling, but Malta weather was great in December, significantly better than Rome where I went just after.