Backlist conversions vs frontlist plans
You will probably have three different kinds of products to consider:
Backlist titles converted to basic PDF or epub. You need to do these conversions en masse and very cheaply. It may be worth choosing which titles to spend time and money on converting yourself, and which to leave to projects like Google Books to handle. (Leaving Google Books to digitise your books may, in some interpretations, class income from those books as subsidiary rights revenue. But since you don’t pay for the conversions that might be worth it.)
Titles in progress. These are a long way down the production line, and there may be little you can do with them other than convert to PDF or epub ebooks when they’re done. How much more you can do (e.g. adding thorough metadata, clearing third-party rights, hyperlinking text) depends on the skill of your in-house production staff.
Title on next year’s frontlist: This is where the real decisions lie. Are you going to create premium, enhanced editions for the iPhone, iPad, and Android devices? Are you going to embed video in your epubs, or experiment with bundling extra content with the ebook edition? Are you going to create tie-ins between the hardback and ebook editions that increase perceived customer value? Or are you going to keep overheads low and simply create really well-structured PDFs?