But do check the ingredients... some flavors might sneak it in. I know the chocolate fudge one is safe.
As for the cake mixes, I heard rumors that DH cake mixes now have dairy in them, but I'm not sure. To be totally honest, it's always a dairy derivative - not straight-up milk - and in with all the soluble fiber from the flour, it never bothers me, and I'm SUPER-sensitive to dairy. So I'd say give it a try anyway, but I'm daring like that. If you'd rather not risk it, read the ingredients on other cake mix brands and see if you can find others that are dairy-free.