A much more viable option for both your patients and your future business/employability opportunities would be to work say 3 days a week year round than be able to take each and every summer off.
While having an entire summer off is desireable as a parent, many, many of those same parents also want to get their kids for dental work (if they need it) during those same summer months. And while in some offices, there may be some months that are traditionally slighty slower than others (business wise) there's never really a downtime in dentistry.
As an employer, if I had a person applying for a job as an associate and they told me that they wanted to take every summer off, I'd very likely NOT hire them, since you're spending the other 9 months a year to BUILD a patient base, just to "ignore" them for 3 months??? Not a good business model.