Keeping motorhome cool back of cab

Hello,

Having completed our first trip to France and being fairly new motorhome owners, we wrongly assumed that the air con in the front cab would come through to passengers travelling with us in the mid/back of the motorhome. How wrong we were! For our passengers it was relenting heat, despite the roof fan in the dining area being on. All through the trip we made sure we parked in shaded pitches, kept curtains closed, windows open etc and managed fine, but as soon as we hit the road in the 30 c heat, it would quickly become a sweatbox and we just couldn't cool it. We are thinking of changing our motorhome next year so don't want to spend too much on systems, but hoped there might be a trick we're missing? Perhaps a fan that is useful or something else we should be doing. We're taking our dog this time too and thought of air con, but realised it wouldn't work when travelling either. We're driving a fair distance so would really like to get things nice and comfortable for passengers and the dog! 

We have an auto trail apache 700 se.

Thank you,

Michelle