8 days Croatia/Bosnia Itinerary

Here's my personal opinion. I wouldn't do the day trip from Dubrovnik to Montenegro. Are you talking about Kotor? Kotor is OK, the scenery is nice if you do the walk up to the top of the hill/fort, but the old town itself pales in comparison to Dubrovnik. I think you will be underwhelmed visiting Kotor from Dubrovnik.

My recommendation is to spend that night in Mostar or add an extra night in Sarajevo. As it stands, you really only have one day (and two nights) in Sarajevo, and to me that's not long enough. Sarajevo is a fascinating city, steeped in history, with a lot of interesting things to see. The tourist office does a good one hour-ish walking tour of the old city and a bus tour out the the tunnel museum. There's also the museum with the exhibits on the recent war. I think Sarajevo is worth 3 nights, or at least 2 nights and 1.5 days if you stay the night before in Mostar and get to Sarajevo by mid-day. Just my opinion. I haven't been to Hvar or Korcula so can't comment on that.

I completely disagree with mattlv Kotor is fabulous!! If you like the idea of hundreds and thousands of people crammed in Dubrovnik Old Town unable to move than sure but Kotor still touristy and crowded is by far more enticing. Paying 40euro for a dorm rooms in Old Town Dubrovnik compared to 15euro in Kotor Old Town I know what I would choose.

May not be such a great doing a day trip you should at least stay a night but you short schedule is rushed and you dont leave yourself much time to explore and enjoy!

On this mattlv is correct Sarajevo is fascinsting and you should at least deficate 3 days here!

Maybe rethink exactly what you want to see/do the most and alter your plans accordingly!

By the way, I'm not a huge fan of Dubrovnik either, especially in the summertime. Everything #2 says about it being overcrowded is right. I wouldn't want to spend 3 nights there.

"Should we do Hvar or Korcula? "
It depends on your travel dates. The Hvar - Dubrovnik ferry runs only twice weekly (Tuesday and Saturday), whereas the ferries/catamarans from Split to Korcula Island (Korcula or Vela Luka) run 4times daily.
The Korcula - Dubrovnik bus runs once daily.

The truth is that the connecton of Hvar and Dubrovnik is not the best and the ferry does not go often, but if you manage rather visit Hvar, a few years ago it was the most popular island for vacation, and has a wonderful camp where isn`t so expensive to stay and it is possible to rent bungalows that is much cheaper than the Apartments and equally comfortable. But if you are staying in Dubrovnik rather first check accommodation and prices. This has become an extremely popular place and also quite expensive. The city is beautiful and mostly lives of luxury tourism, but it's worth to see. There are various agencies and accommodation providers, we found accomodation in Dubrovnik apartments and it was satisfacting.