thanks for the advice. What dou you mean by steer? What must I do paddle or what do I do to steer?
The first part of your paddling stroke is normal. Somewhere between a halfway and a almost finished stroke you twist the blade sideways. It now acts as a rudder, allowing you to steer. Push it sideways. Normally that would be away from the canoe, but any move that gets you where you want to go is permitted.
If you need to steer the other way you may also just put the paddle on the other side of the canoe.
Do a quick google video search for "canoe J stroke" or "canoe L stroke" and you should have plenty of ideas to different things you can try out with your oar. (One example here, just the first random google link I found: http://www.redrockstore.com/Jstroke/index.html
Paddling is teamwork. In a perfect world, the effort of front and back paddler is balanced so you go straight. In the real world, the back padler has to compensate some way or another. The front padler dictates the rhythm of the strokes and the rear padler is the one that steers.
I thought the bow had to be deepest in the water that is why I put him up front.
No, it's the other way around, the rear should be deeper or the boat becomes impossible to steer. We're not talking about excesses here - an inch deeper in the rear than in the front is plenty. Maybe as little as half an inch. Try it out and get a feel for what works best for you.
Should I put some extra weight in the boat next trip?
Possibly. If you keep your husband in front, absolutely. If he goes to the rear extra weight probably isn't necessary.
Rhine... deep ... I dont want to tip there at all.
I can understand that ... but there's really no reason for you to tip unless you deliberately push the boundaries. Nevertheless, with all the traffic on Rhine I'd stick close to the river bank.