The trend nowadays is to get a set of cordless phones for the home for the convenience of being able to answer the phone anywhere including the garden.  Their range is usually not affected as badly as Wi-Fi is by walls or obstructions.  You can get them in sets of up to five handsets to make them as convenient as possible. 

However be wary of a disadvantage with them.  If the master of your handsets loses mains power the whole system is rendered useless.  It could simply be a matter of someone unplugging the master to use socket and forgetting to re-establish its connection, or the power might go off because of a local problem, or if you live out in the country power cuts might be a regular problem. 

Just in case any of these are a  possibility and if you value having a lifeline in case of an emergency then simply plug an analogue corded phone into a spare socket.  It will always work even if you have a power cut.  If the local telephone exchange is affected by a power cut they have batteries to take the initial load and then generators kick in to ensure the equipment is still powered as you would expect in an emergency. 

If you don’t have a spare socket to plug that analogue phone into then give me a ring and I’ll be happy to come and rectify that.