Croatia, Montenegro, Bosnia itinerary for 10 days, input needed

I would not combine Montenegro with Mostar into one day on May 12. Do all your Montenegro sightseeing on May 11, the prior day. You pass Perast driving on the way to Kotor so it doesn't make sense to put it off for another day - see them both on May 11, and whatever else you have time for in Montenegro. I would squeeze Cavtat to another day and use that extra day for Mostar. It's worth spending the night there (Mostar) on May 12, and driving back on May 13th. Cavtat is not really a destination but a nice town outside of Dubrovnik, I'm not sure it needs an entire day (you can combine it with Dubrovnik, say on May 10th). Mostar is simply more significant, and different from the other places in Croatia, to warrant more time than your schedule gives it.

Just a "heads up". From Kotor there is a road that leads away from the bay inland. The views are spectacular. But, It goes up the side of a steep mountain and has 25 numbered 180 degree switchback turns and at least 75 other sharp turns. Rock wall on one side and nothing on the other. Can't remember the name or number of the road, but it went to the towns of Njegusi and Cetinje. Don't mean to rain on you parade, but don't want you to get into a hairy situation without any knowledge. If anyone in your party is prone to motion sickness or has a problem with heights you might want to avoid this road. You can go to bing.com, use the map feature, and see aerial views of the road from &*$$. You can also check it out on googlemaps.com.

Additional info: On 12 Mar. 2017 there was a thread titled "Greece Montenegro Croatia". One person included a link to the map that shows the road. Another person had a link to a video made along parts of the road.

I prefer Korcula over Hvar. Hvar seemed like a place for rich people to show of their yatchs, but Korcula had more charm in my opinion. Plus I'm a sucker for city walls.
And yes Perast is tiny and on the road to Kotor.
The old road from Kotor to Mt. Lovcen offers absolutely stunning views over the bay of Kotor. It's a bit windy, but I did not feel it was particularly hairy.

It's a quick pace, but if you like traveling that way, it is certainly feasible.
You will have to determine if your rental allows travel to Montenegro and Bosnia.

You won't encounter TC's road on the Dubrovnik-Perast-Kotor drive or the Kotor-Mostar drive. For the latter, ViaMichelin offers an inland route that would give you a look at a different part of the area as opposed to partially retracing your steps. I haven't traveled on that route, but part of it is marked as "scenic".

I don't think you'll have time for an additional stop on the way to Kotor, but Herceg-Novi is very nice. It's quite a bit larger than Perast, though, so really not a 30-minute stop.

Thanks for your input. I have added a few days and tweaked the plan to:
May 3 arrive Split, drive to Plitvice
May 4 hike Plitvice first thing, drive to Trogir
May 5 explore Trogir half day, explore Split second half, return car, overnight in Split
May 6 7:40am ferry Split to Korcula
May 7 Korcula
May 8 10:10am ferry to Dubrovnik arriving 12:00, hike wall, Karaka Panorama boat cruise
May 9 Dubrovnik, Mt Srd
May 10 rental car, drive to Kotor, stopping at Perast and maybe Herceg-Novi, overnight Kotor
May 11 drive to Mostar, overnight Mostar
May 12 Mostar
May 13 Mostar to Blagij, Pocitelj and /or Kravice Falls to Cavtat for overnight
May 14 6am flight out of Dubrovnik

Any more input is greatly appreciated!
Cheers,
Donna