Kim Kaupe, co-founder of ZinePak wrote an article with some good tips for planning for vacations (for yourself and employees). Check it out at Forbes.com: "The Quick-Tip Holiday Playbook For Busy Entrepreneurs".
One of Kim's points is also very appropriate for preparing for a business sale: "If you are not able to take a vacation, it means you have done a poor job as a manager. Your business should be able to run without you if you’ve done a good job at setting up systems and structures." If you are able to take a totally un-plugged 2-3 week vacation and come back to a business that's running as well, or better than when you left, business buyers will perceive your business to be far more attractive and valuable.