We've only taken the kids 3 times. First was a Mediterranean cruise and that was the least favorite. Mostly because I hate big cruise ships. We also went with my ILs which was part of it too. There are spots I'd like to revisit...Barcelona and Cassis in France. We started in Rome and Rome is great, once. So touristy and I can only handle so much of the excessive crowds.
Greece was amazing. A wonderful mix of relaxation and history. We did Santorini (other islands would be just as great), Crete (2 spots...Chania and Elounda), and Athens. We did a lot of boating and beach time. Walking around Chania (Venetian style city). Athens was a lot of touring. Food was amazing. This might be our favorite in Europe, but it's close with...
Northern Europe...Sweden (Stockholm may be my favorite city we've visited so far), Norway (did the fjords), and Copenhagen. We used a travel agent to book tours for the ages of our kids at the time, which included a few Viking related tours.
Mama to my boys (04,07,11)