This is a tough one. I agree with waiting to be asked and being vague. Personal, family reasons should cover it. Follow up with assuring them the time gap is no issue to your readiness to do the job. Draw attention back to your strengths and the gap will be a non-issue.

The down side to setting up a business to explain the gap (other than the ethical question... or the 'what webs we weave.....) is the likelihood that potential employers will want some customer feedback information. Your business' customers become the equivalent to a past employer or any other professional reference.