My other idea/option is to let them expire, delete and the purchase them again for a teaser rate. (With clear cut plan to develop them in order to justify next year’s renewal) Obviously I would not risk this "penny wise, pound foolish" mentality if these domains even ranked, had PR, or even significant traffic. All though I think the names and categories are good, I'm not too concerned that these would be snapped up by someone else. Has anyone risked or experimented with this option before?
Ideas are great, but too many can be the "albatross" around your neck. Focus on the direction you want to go and sell the rest or just let them die. This business is full of distractions and they often keep you from realizing your goals.
Good luck to you.