For a nice, fairly moderate hike in Westlake Village, take Triunfo Canyon Road south to Highgate Road and head up to the southeast endpoint of Highgate, past Hillsbury Road, to the end of the road, where you'll see a trailhead sign. Park on the street.
It doesn't actually say "Lake Eleanor Open Space Hike" but this is indeed the way to get to this trail maintained by the Conejo Open Space Foundation (COSF). Walk past the fence on the pavement, and in about 60 steps, the trailhead is on the right. There's no sign. In fact, I've never seen any signs indicating which way to go on this trail. But once you reach this path, for the most part the trail is pretty obvious.
COSF has some helpful images and a trail map at cosf.org/trails/other-trails/easy-lake-eleanor-open-space-hike.
There are some brief, slightly challenging hilly sections on this hike, along with some rocky sections, but for the most part, this trail is perfectly fine for all ages. I generally wouldn't recommend strollers on this trail though because of these sections, but if you have a solid off-road stroller, it is possible.