Don't think it was mentioned, but you should check out
Rick Steves books on Europe to help you make a decision on where to go and when. Any library or book store will have them. Of course, once you start digging into the history, charm and beauty of Europe and its people, you will realize that you can't do it all in a week or two. You folks are young enough that multiple trips there over the years should be possible. That's how we are doing it. I was stationed in Germany for 31 months with the Army many years ago. I visited 17 countries during that time and still didn't see it all. Discovered Barcelona on a
DCL B2B last year and wished I had visited there earlier. But there are other parts of the world to see...to say nothing of 50 states here at home. Look at your interests (hiking, dining, churches/cathedrals, forts, ruins, etc.), decide what you can afford, narrow down the list to what is practical time-wise and go for it. For your anniversaries you can always go back for more.