UPDATE:
Looks like we'll be 4-6 weeks down there, more precise most of the time in Gabrovo, at least 1.5 weeks in Varna / Slynche Brag (Golden Sands) / Somewhere near a beach.
Got some tips who to contact reg offroading, but would need at least one other car in case I got stuck or something (our baggage is Dog, Child and Wife, means we need the car...)
I could try arranging lodging or hotel (wife has someone who can get a discount for proper hotels. Last time we had a full apartment, about 60sqm, with kitchen and nice bathroom for the two of us, but that was not during the season)
If someone's interested, please PM or email me.
If I find someone to do it with, I'd propably like to got the route via Italy near the sea, either on the way there or back.
Cheers
Phil