Home Router Challenge!

So I'm updating my home router, however our situation makes this task a little overly complex, we've got a multi-level home with tenants in separate suites that need to have decent WiFi coverage, as well as several devices connecting and transferring data simultaneously (I add this because our current model has trouble maintain over five simultaneous connections) The number of devices that would most likely connect simultaneously is seven (2-3 for netflix), however that number could go up or down. So what router would you suggest that could handle this with minimal tinkering?