Some people hire out their goats to clear properties of weeds. Goats will definitely eat poison ivy, although they will also eat the landscaping, so if he wants to keep anything leafy, goats wouldn't be an option.
A pair or so of goats could clear a backyard in an afternoon or two. And no chemicals left behind. :)
You should consider calling a professional landscaper to help you remove the poison ivy plants. One of the best ways to avoid a poison ivy rash is by simply avoiding contact with the plant. Getting rid of poison ivy plants can be extremely dangerous, since the plants often grow back; this get you exposed. Visit http://pediatrics.about.com/cs/conditions/a/poison_ivy_3.htm for more ifnormation.