That sounds perfectly reasonable and like a great trip. Croatia is a great and beautiful country and in terms of infrastructure definitely on par with any other Western or Central European country nowadays thanks to huge tourism booms in the last decades (mainly Germans and Austrians).


No need for a ferry really, you can just drive over by car via Slovenia. Be careful, even the few kilometres of Slovenian motorway you'll have to cross require a Vignette (toll sticker) for around 10€ or so and both Police and Toll Control are out there in the hundreds taking your money if you forget to buy one.

I can recommend Novigrad, Porec and Pula in Istria which are all absolutely lovely and stunning towns and with you coming in October you'll have the additional advantage of avoding the Austro-German hordes sieging those cities in the summer months.

From there you could continue on onto one of the many Croatian islands, nearby Krk and Rab spring to mind.


Enjoy!