There really is a difference. First, paved roads are usually better maintained, so it is safer and easier to ride faster (less potholes, cracks, debris to avoid). Second, roads are designed for faster traffic than paved trails.

Is the trail a multi-use trail, or is it intended JUST for bicycles? If it's multi-use, the picture changes significantly. If so, find out what the trail speed limits are; they may be much slower even than your "slow" pace! Why? To help protect the other users of the facility, which may include children, senior citizens, pets, etc etc.

I just took a very good class on bicycling on the road. Most urban areas have groups that sponsor such a thing - may I suggest you and your husband seek one out and take it together?