I’ve spent 5 out of the last 6 summers driving over Europe for holidays.
We’re big fans of the German/Austrian alps (so much so that we’re heading back there next year) but where you gain in the shorter drive, you lose in terms of pricing. Is cheaper than somewhere like Annecy in France though.
We spent one summer driving to Slovakia to stay in a friend’s chalet/business (mentioned above). I’d go back to that area every year, if it were not for the long drive.
We went via Poland going out (staying in Zakopane).
Used to work for a Slovenian company and have been there before too.
Realistically, I don’t think you’ll be disappointed at any of the places mentioned so far.
Prices vary slighty – your money will go further in Slovakia then Slovenia (and even further in Poland).
Having holidayed in the French Alps, I found that holidaying in Poland/Slovakia meant that we could afford to eat out every night and do activities most days because of the cheaper prices.