what about overloading the car? the c4 is not huge and i presume it has a total weight limit (whatever that is called)? With 4 bikes and the carrier on the back and a full roof box, family and luggage you may well come very close to this limit…
They weighed a car once on breakfast tv, roof box and few bikes on the back, family of 4 packed for holiday. I think it was near or over its limit (not ever 4 bikes and small kids). Insurance companies will try and get out of paying…
Perhaps get a bigger car? No roof box and bikes on the roof (again, watch the weight limit of the roof), sorted!
I used to drive an old vauxhall omega, those were the days! Stick it all in the boot! had to get rid at 19mpg in town.