Thank you all for your amazing answers.  So helpful!
acraven, What a great idea to fly into Venice.  I have only been to Venice (on a cruise) so of course never got to spend a night there.  This sounds like a perfect opportunity to do that.  
jlschandler and Barbara, thanks for the information on the GoOpti Shuttle.  I will check that out.  Flying out of Dubrovnik and into Zagreb to connect in Amsterdam and back to the US sounds like the best plan for leaving.  May I ask.....did you stay overnight in Zagreb?  I am always leery of connecting on two different airlines (unless Croatian is a SkyTeam member, which I don't think it is).
Barbara, I am so glad you enjoyed both tours.  I can see where you would get more out of a place the second time around.  I love RS Tours but sometimes things go really, really fast.
Andi and jlschandler, Bosnia was one of the places that drew me to this tour.  I was a high school teacher when of this stuff was going on and I did talk to my students about the war so I know a little bit but it would be nothing like experiencing this amazing place (Mostar) in person!  I read somewhere in the forum that someone said it was "just a bridge" but I am sure it is so much more than that.
Unfortunately I won't have much time after the tour is finished because I am leaving for China two weeks after this tour ends.  I have been to Montenegro and loved it.  Again, this was a cruise and sailing into the fjord (well, not officially a fjord but it sure looked like one to me) was a sight I don't think I will ever forget.  Cruising into Kotor, Venice and Sydney, well, those are truly into iconic moments that can only be experienced from the sea.