Hi
We also go every June and stay in St. Marie du Mont, which is exclelent place to be with the camp and the night time entertainment, Never really had any issues. Just take the normaly spares and ensure you check over the vehcile before going and give a good service. We trailer down to pool and drive on the ferry with the jeeps and drive from Cherbourge, takes about an hour. Ensure you fill out the custom forms think these are then picked up by your passport and number plates from what i understand. We always take Wepons and never have any issues just need to book them on the ferry in advanced.
Your more than welcome to tag along anywhere with us we have some good routes and things to see by jeep.
If i can be any more help drop us a PM