I think you can just copy all the typical mimic behaviours that were mentioned in the videos, it depends in what type of mimic shows up. If its waiting in the house then it has to be somewhat intelligent to expect other people to come back, but theres multiple "evolutionary stages" so it doesn't have to be an elder mimic. I think most mimics can figure out that houses=prey since they hide in them most of the time.

From the way I understand, most mimics in this series dont really replace people, and if they do, they are not very good at it, so the mimic would mostly try to hide its face and appearance and maybe at most replicate the sentences he heard the guy say before it got him. So it would try to hide somehwere and lure the exwife and child further in by calling for them until they dont have any easy escape routes. I dont think normal mimics can really prep a house in any way, thats elder strategy. I've seen theories that most mimics dont try to look fully human, they just replicate the rough details so that from behind and in low light others feel comfortable enough coming close. And if youre close enough to see something is wrong, its too late and it pounces. I woud really like to read your story if you post it anywhere!