Lake Bochinj is S W of lake Bled and, in our opinion, nicer. There is a campsite on the W shore which is nice - if you arrive on a busy time, get there early afternoon but I guess there won't be a problem with spaces outside of the school hols.
Hi Ian. I'm planning similar in August/September, so let us know how you get on.
Current issue of MMM features a Slovenian trip, quite interesting.
I was at Bohinj and Kranska Gora many years ago, not in van. Beautiful country.