I'm going to be the odd person out and say that I think it is fine for you to wear the dress as you did in the photo. You have great legs, so the length seems to work (although you do seem to have one leg at an angle, so I'm not sure if that makes the dress look longer than it really is). I know you said that it shows a lot of cleavage, but from the photo, it looks fine to me. I wouldn't see you in that dress and think "wow, that woman certainly is showing a lot of skin!" If you were wearing it to work, maybe. But wearing it out to dinner, I don't see an issue.
Of course, as the weather gets cooler, it would definitely look cute with tights, hose, boots and/or something on top. But I just wanted to chime in to say I don't think you *need* any of those things to make the dress acceptable.