Route advice - Dunkerque - Central Italy
Hello everyone 
I am looking for some help and feedback with a route from Dunkerque to Central Italy.
It is for a couple who have a car and caravan, and have approximately a month for their trip.
They would llike to avoid Switzerland completley, and would like feedback on the following route options:
Drive through France, avoiding Paris (going via Reims) down towards Grenoble, and then take the Frejus tunnel into Italy, is this a good route? Would they be better to use tolls roads, or is it a good route to do on non-toll roads?
Their other option is to drive through Belgium, Germany and Austra, does anyone have any feedback on this route?
They definately do NOT want to go over any high passes, they are quite happy with tunnels!!
Any feedback or advice would be appreciated!
Thank-you