For Barcelona, try tapas vascas in the restaurant Txapella, it is in Passeig de Gracia, the main avenue that leads to the main square (Plaza de Catalunya).
This restaurant is specialized in Tapas in basque style. For regular spanish tapas, there are plenty of restaurants, specially if you go down through the Rambla (main touristic street), then take any street to left side, when going downhill. There you find good tapas restaurants. Don't eat in any restaurant in Rambla itself. They are mainly tourist traps.
In Barcelona I advice you to take the city tour bus, and spend a good time to see the unfinished church Sagrada Familia and other architectural works by Gaudi.
If you get tired of Barcelona and you have time, try to visit Sitges (
http://www.tripadvisor.com/Travel-g18750....Info.html ). It is 35km away from Barcelona and you can get there by train, from the Barcelona Sants station.
For Rome, try to eat in simple restaurants. They usually have the best food. Order pasta and table wine, of course. When asked, say you love Ferrari so the doors will open for you :-)
Make sure you visit the Vatican and Colosseum (besides above mentioned suggestions, of course).
If you get tired of Rome (that is difficult), try to visit Tivoli and Villa Adriana (google it for more info). You can also get there by train.
Pay attention that Rome is bigger than Barcelona and you'll probably need to walk more as well, so reserve more time for Rome.
Be careful with your wallet, backpack and camera. There are lots of pickpockets in both cities.
Completely forgot to mention that you should also try to eat Paella when you'll be in Barcelona.
The most famous one is the restaurant Can Majo'. I tried it once and it was very good.
I also had some good ones in the restaurants located in the Olympic Port (
http://www.barcelona-tourist-guide.com/e...-port.html ).
They have different kinds of Paella, so don't be shy to ask the waiter to explain the difference among different types of Paella.
Enjoy it with sangria or wine.
The price of a paella in a good restaurant is a bit expensive, so I advice you to take your future wife for a special dinner in Barcelona and have a Paella. If she likes sea food, she'll love it.