Slovenia or other side trips

We are booked in June of 2017 to go out of Venice to Croatia and Greece. We are looking to add a week on either before or after. Slovenia sounds like fun. Please suggest any other surrounding countries to visit for land tours. Our group is 11 people. Oldest in the group is 51 youngest is 14. We like to walk and see things, love water and just have a good time.

Have always just driven through Slovenia to get to Croatia. I would do a good wander around that country because its a nice place. Loved going island hopping! I can't recommend getting off the beaten path in Croatia enough! :)