Rome or Venice first?

If you were flying from Italy back to the US, I would suggest to depart from Rome (i.e. do Rome last). The reason is that flying back to the US from Venice would mean very early departures and getting to the Venice airport from Venice is neither cheap nor quick. However since you are going to BCN from Italy, it probably doesn't make much difference. It is really up to you. I would look at the flight options and see the convenience of flights with either option. It is true that Vatican Museums are closed on Sundays.

Kim, I like your idea of starting in Venice, just experiencing the city as you adjust to the time change. I believe you're also correct that many Roman museums are closed Mondays, but I could be wrong. (We were there Tuesday-Saturday.) If the airfare isn't a lot more, flying a day early can only be a bonus! There's plenty to see in Barcelona. And it does give you that "safety factor". Oh - check out "Air Berlin"...they often don't come up on travel websites, and they fly from SFO only a few days a week, but it's easily as nice as American or United. Our airfare on Air Berlin was easily 1/3 less than other airlines. Be sure to get Rick's "Italy" book - it will help you choose sights to see. It also includes "walks" through Rome that allow you to see numerous things within a few hours. I'm jealous! Dave

It's a shame that there are no San Francisco to Italy direct flights. It makes for a long day for Californians flying out to other European airports and transferring for flights into Italy. I too think you'd do better to start in Venice and end in Rome. The Rome FCO airport has Vueling Airlines going to Barcelona, and they're a good budget air carrier.
Have a great cruise.

Thanks for the advice. The more I think about it, the more it seems to make sense. We will likely be changing planes in Frankfurt anyway, if we are able to get miles tickets on United, so going to Venice is no big deal. I think starting in Rome with probably our two most intensive sightseeing days of the whole trip, right up front, might throw my little one over the edge. He is 8 now and always says he likes to relax on vacation, not rush around! Hahaha! So maybe we better start with the couple days where we can just take it slow. The hopefully I can coax him into picking up the pace a bit in Rome. Thanks!
Kim

Your second option is much better~ With an 8 year old boy, make sure you take him to the colloseum! He will love the Gladiators, and I think there's even a "gladiator school" I saw a few months back on this thread a month or so ago.
You could re-post that question and see if you get a response. Also, in Rome there's the Piazza Navona, and they have a lot of vendors selling fun and inexpensive toys. Across the street from the entrance of the Vatican Museum, the best gelato (and biggest servings) is Old Bridge Gelato. Make sure to take him there as well. Very good pizzeria also down the street from there. If you feed him just before doing the Vatican you may be able to avoid eating the bad and over priced food inside the walls. When looking for pizza, look for "forno al legno" on the board/menu. It means wood oven, and it's usually much better. With a cruise, always, always arrive at least one day before the departure especially an international flight. Flights have been known to cancel because of weather/mechanical -- and an extra day to adjust to the time is also nice.

Venice is one of the best places to start a trip. You can relax and soak up the atmosphere, instead of running around trying to see the sites. Take the vaporetto (water bus) up and down the Grand Canal. Most of them have seating in the very front (best) and in the very back (second best), and if you are patient, you will be able to snag these desirable places, and just watch the city glide by, once in daylight and once after dark. If you have jetlag and are up before dawn, go out on the vaporetto before breakfast, to St. Mark's Square and watch the sunrise over the lagoon. I've done a lot of taste-testing (in the interests of science, of course) and Venetian gelati are much better than Roman ones. The Vatican museums are closed on Sunday, most other museums in Rome are closed on Monday, so the Vatican museums are really crowded on Monday. I think you are right to get to Barcelona with enough time before your cruise. It's worth the peace of mind to lose a day in Italy. Besides, it's been around for millennia, so you'll have other opportunities to visit. And you never know, you might really enjoy Barcelona just as much . . .

Forgot some fun things to buy for boys in Italy and Spain (I have 3 grandsons)
Italy: Pinocchio marionettes -- they're sold in both Venice and Rome around the Spanish steps site, gladiator toys. Chess pieces. get the board at home, too heavy to transport home. Model cars are beautiful! Spain: tiles that spell out their names. (My grandsons have never outgrown these, they're still hanging in their bedrooms)

Thanks all! Yes, I am thinking this should definitely be the plan. I am going to change my "official" itinerary. I am really hoping to talk my husband into leaving Thursday night, this giving us the Italy time I want plus get to Barcelona on Thursday. But if not, I am still struggling with whether it's ok to get to Barcelona on Friday early, with cruise leaving Saturday afternoon. I think that's enough time, but.... not sure. I would never come all the way from the US and get there on Friday, but somehow from Rome seems safer to make it in sometime on Friday. We could also adjust after cruise and spend the day in Barcelona before heading to Munich if we want more time.... I saw that gladiator school one too somewhere and that is totally on the list! Kim