If you decide to go to Terezin, I suggest using Wittmann Tours, and if possible with Helena Katzlingerova-Rakytkova ('Helen') as your guide. Helen, who has been guiding for Wittmann since its inception over 20 years ago, gave a fantastic tour for my wife and I in late August 2015! It was supposed to be a group tour, but it ended up being a private tour since we were the only customers that day. And Helen took us to places that I did not see on a previous tour of Terezin with Wittmann in 2007, such as inside the walls of the Small Fortress. Helen is extremely knowledgeable about Terezin and has personal ties to a survivor, about whom she and her husband wrote a book (Life Forbidden, by Jan Rakytka - about Prof. Felix Kolmer). I don't think one can say that he or she 'enjoyed' a visit to a former concentration camp, so I will say that it was extremely informative, historical, thought-provoking, personal, and sad when one realizes that most of the Terezin prisoners did not survive the war.
In late August 2015, we also took a day trip from Prague to Dresden with Kamil Vondrous, who with his wife Petra, owns Prague-extra.com. Kamil was an excellent, knowledgeable guide, who was friendly and engaging. The cost of the 10-hour trip was very reasonable, especially compared to other trips with private guides that we have taken in Italy and Denmark. We very much enjoyed our day together and would highly recommend him if you are looking to arrange a private tour in or out of Prague