a few comments for those that had asked me our impressions, hoping to contribute some useful information.
Barcelona:
We knew that traveling with kids in the winter is not ideal, but we were lucky and we had wonderful weather, sunny and mild. It is of outmost importance to have a well located hotel because daylight is short and there is more need to rest indoor.
The most difficult aspect of traveling with a child has been to adapt to the late eating schedule and to the crowds. We did not realize how popular Barcelona is. Everywhere we went we only heard Italian and French. While for a group of adult friends it can be fun to climb a crowded bar stool and have daily fried squid, it is not pleasant to have to squeeze your tired child through the throngs that invade any restaurant , tapas bar or market stand at meal times. Around Pinoxto at the Boqueria each person was eating with other three people waiting for their chair . How worth an effort is even the best fried squid in the world? We fled.
Restaurants open really late. Some as late as 1:30 or 2: p-m. for lunch and 8:30 or 9:00 for dinner. We had to miss some of our planned restaurant because we simply did not make it to wait so late. And we did make an effort to adapt (late breakfast, snacks, etc.) but winter makes you hungry, so we ended up at the Chinese buffet
Attractions are really quite scattered throughout the city and suburbs (e.g. Park Guell) so the traveling time is significant even though the public transport is efficient. Going with children means getting resigned to miss some of the important sights. On the other hand it was a really luxury to have the waterfront which made for long pleasant walks in the tepid sun. The whole waterfront is beautiful, modern, clean and safe, just ideal for the family.
Speaking about safety: We had our worse clothes and everything in our pockets, one ugly bag for the guidebooks. It either worked or we were lucky but not for a second we felt unsafe anywhere or were aware of someone attempting to pickpocket.
Seville: beautiful, easy and beautiful. What can I say more: beautiful. The city centre is quite compact so we could walk everywhere and get back to the hotel for rest whenever we wanted. Definitely a much better place with children but one has to be lucky with the weather as there are few indoor attractions. Tip: little girls love the flamenco outfits. Mine preferred a hair-clip with a rose and a fan but the little flamenco shoes are irresistible!!!!
I have just submitted reviews for the two hotels/B&Bs where we stayed. In Barcelona, we also spent 3 nights at Hostal Girona for lack of a better alternative (pricewise) but we do not recommend it.
Slow Travel Talk 
