D9, in my case my neighbors and my parents dropped in at my house at any time of the day! And yes I did check their bags, and my other kids were older when I had one. My youngest was 9 months when I started and my oldest was 9. I explained about Kashrus and milk and meat and I had two separate sides. And if my kids told me something that didn’t sit well with me I let her go.
Today I have 3 separate sides, one even for Pareve with 3 sinks and 3 ovens and dishwashers. She knows she can’t turn on the fire and if no one is home in my house she goes next door to get a neighor and at this point my youngest is 24.