Traveling from Vienna to postojna tomorrow

Hi, I will be traveling tomorrow to postojna from Vienna with my family that includes kids ages 12, 14 and 17. I would like to include a stop somewhere fun and beautiful to do something like rafting or if that nature with the kids. What do you recommend? Maybe a stop in Bled?

Also, I see that the postojna caves close at 18hs tomorrow. Is that when I can last get in or when I need to be out by?