My opinion is that people live in fear of all the wrong things. Even if there is a Cougar in the neighborhood, your child is at much greater risk on the road in the van than in your yard next to it! Very few Cougars attack people. However, it certainly has happened and some sensible caution would not be out of order. I wouldn't let a four-year-old play outside unattended anywhere. This would be a good time to start teaching your child appropriate behavior in case of a Cougar encounter. The site below has some useful information. What else can you do? Move? Have the Cougar killed? I think either would be inappropriate.