which 6 berth?

hello all, new to the site and hope all you pro's (geeks?) can help us.  We have four children ages 7, 6,4 and 9 months and intend to spend June to August travelling down the west coast of France and into Italy. 

We want a caravan with an end bedroom and fixed bunks with the dinette that turns into a double so all the kids can be shut in at night and we can cook, listen to music etc without disturbing them much.  We have seen a couple of 6 bert with this set up but they all seem to be soooo long.  Like 22-24 ft.  Will this be a probelm on coastal roads and also to pitch on Eurocamp sites and similar.  Or is there an alternative van with an end bedroom for 4 thats not as long.  Needs to be a big double at t'other end too as we are both tall.  Am I asking too much? 

we have previously stayed at Eurocamp sites in Brittany in static caravans but want to go further.