Sites in Germany?

We will be going to Austria this coming summer to stay on a lovely small lakeside site we found last year at St Wolfgang (before we bought the 'van). This will be our first trip into Europe towing the 'van although have driven abroad on numerous occasions. We have already found a club site at Rudesheim to break the journey south and are thinking of staying a couple of nights around Lake Constance before heading east to our main destination. Can any members recommend any sites around the lake (preferably on the German side) and also any sites for heading back north so we do not repeat the outward bound route? My wife is German so language is not a problem however the sites do need to be dog friendly. We do not have children so small quiet sites would be ok (ideal!) for us.