Have you and your husband discussed what you would do if the woman is MORE into one of you than the other? I understand you'll only date together, but what if she likes your husband but REALLY likes you? Or likes you but REALLY likes your husband? You can't make someone have feelings of equal intensity for both of you. Is it okay if she develops stronger feelings for one of you as long as she also cares for the other?
Also.. Are you going to have a few dates just you and her and just him and her later on after you've gotten to know each other a bit? I think dating a couple would be an interesting experience (probably never going to happen since I'm married and most couples want a single woman), but I would want to have alone time with each of them at some point.
Anyway... I think being more direct is probably a good idea, depending on what you're thinking. What are you saying that you are wondering if she is reading between the lines? Is it something about intentions of how the hopeful relationship will be? The dating process? It's better to leave no question about those kinds of things. If it is about how awesome you think she is so far and how you think you'll be together forever... Vague is probably okay and even better so that she doesn't think you're jumping too fast.