As a non-kid haver, I'm gonna argue here that age 8-11 is the best window to hang out with other people's kids. I had some family in town recently, including 8-year old nephew Patrick. Most of my favorite moments from the visit were spent just me and him, walking the dog and talking about stuff he's seen and stuff he thinks. No toddler fussiness. No teenager attitude. At this age, they're just cruising around being little humans. It's refreshing.