Some point I would make on a few of the cities you are going to visit. Barcelona as well as most of Italy have pretty good pick pockets. Normally it is not usual to have the serious physical crimes we may experience in the US but they have real good pick pockets. It is recommended you keep the purse under your sweater, etc. so it is does not show. For men it is best to keep the money in the front pocket with hands in the pocket. They do not think twice about cutting belts on fanny packs, etc. This is not to over state it but it is best to be cautious as we are not as exposed to great pick pockets.
We have been to Naples a couple of times and had a great side trip to Sicily. If that is an option I think it is worth it. Regarding Rome. Depending how much time you have in Rome the On/Off bus is terrific. You can see the best of Rome and enjoy getting off at various stops and then getting back on. Nice was fine but I found it as a walk along the beach. If available a trip to Monte Carlo is fun and you can go into the Casino where some of the Bond films were set and actually put a couple of dollars in their slots. Of course not everyone agrees with each others trip fun so these are just a couple I liked. In Rome there is a great little resturant at the Spanish Steps. It is upstairs overlooking the steps and a good rest stop if you are tired.