32 feet is a standard ladder size. In this situation you would just strap a wooden slat across the top of the ladder before you raised it. Then it would be supported on two poles.
And yes you can even get 48 foot and 60 foot ladders. But they cost a chunk of money.
A 30 foot fence would be a impossible task to ladder your wife and kids over. Once on top, you have to rope them down the other side. Try balancing yourself on top of the fence while dropping your 80 lb ten-year-old down the other side on a rope. Would the wife be able to rope herself down? They would have one chance to do it right.