One of the easiest ways to protect your children or grandchildren is to add TR (Tamper Resistant) Receptacles.
Here is a video that explains these receptacles. http://www.childoutletsafety.org/video.html
Here in central Ohio Northwest Electric and Plumbing (OH. Lic. #26286) installs these for as little as $10.00 each. Yes there is a minimum charge. Or you can replace these yourself if you have a working knowledge of residential electric.
You could as a Realtor offer to have these replace for your client to help make a sale. As you can see it is not pricey.
You can reach Northwest Electric and Plumbing at 614-214-1487.